Nearly everyone experiences fatigue, but some professions, such as aviation, medicine and the military, demand alert, precise, rapid, and well-informed decision making and communication with little margin for errors. Recognizing this, the National Transportation Safety Board (NTSB) added “Reduce Accidents and Incidents Caused by Human Fatigue in the Aviation Industry” to its list of most wanted aviation safety improvements two decades ago. Specifically, the NTSB called for research, education, and revisions to regulations related to work and duty hours. Regulatory change has received the least attention, with no changes to relevant regulations since 1985 despite a significantly expanded research base on sleep, fatigue, and circadian rhythms.1
Concern about the potential contribution to fatigue from time spent commuting to a duty station was elevated following a fatal Colgan Air crash in Buffalo, New York, February 12, 2009. The crash, and the first officer’s cross-country commute, received substantial media attention. The NTSB determined that the probable cause of the accident was “the captain’s inappropriate response” to a low speed condition (National Transportation Safety Board, 2010, p. 155). The NTSB report identified multiple contributing factors related to flight crew and corporate factors, but did not list fatigue or commuting as a contributing factor or cause in the accident. Instead, the Board concluded that “the pilots’ performance was likely impaired because of fatigue, but the extent of their impairment and the degree to which it contributed to the performance deficiencies that occurred during the flight cannot be conclusively determined” (National Transportation Safety Board, 2010, p. 108).
Against this backdrop, in September 2010 Congress directed the Federal Aviation Administration (FAA) to revise its regulations related to work and duty hours to reflect current research (P.L. 111-216). The law also directed the FAA to contract with the National Academy of Sciences (NAS) to conduct a study of the effects of pilot commuting on fatigue. The NAS was directed to review information in seven specified areas. Based on that review, the NAS was charged to discuss relevant issues with the goal of identifying potential next steps, including possible recommendations related to regulatory or administrative actions or further research that can be taken by the FAA: see Box 1. The FAA issued a Notice of Proposed Rulemaking (NPRM) on September 14, 2010, inviting public comment that would be considered in issuing final regulations. The NAS study is designed to inform the component of these final regulations relevant to pilot commuting.
The NAS established the Committee on the Effects of Commuting on Pilot Fatigue (see Appendix A) to conduct this study. This interim report highlights key findings from the scientific literature on fatigue in relation to time awake, time asleep, and time of day; identifies issues the committee will need to consider; specifies the information available to the committee to date; and presents the committee’s plans for collecting additional information. The committee’s final report, expected to be issued in summer 2011, will present its conclusions and
1A Notice of Proposed Rulemaking (NPRM) with revised regulations on this topic was promulgated in 1995, but it was withdrawn in 2009 with the acknowledgment that changes since 1995 in both the world of commercial aviation and the scientific understanding of fatigue had rendered it out of date. A new rulemaking activity was started that resulted in a new NPRM issued in 2010. The committee discusses this FAA rulemaking activities related to flight crew fatigue in a subsequent part of this report.
recommendations based on the information available during the course of its deliberations. It should be noted that this interim report is being provided according to tasking requirements, and that nothing in this interim report should be construed as findings, conclusions, or recommendations from this committee regarding pilot commuting. Rather, it is intended to provide a snapshot of the committee’s activities to date, and to present in broad terms a “road map” of how the committee intends to address the issues in its final report.
Information to Be Reviewed and Study Objectives
The study is to review available information on:
- the prevalence of pilots commuting in the commercial air carrier industry, including the number and percentage of pilots who commute greater than two hours each way to work;
- characteristics of commuting by pilots, including distances traveled, time zones crossed, time spent, and methods used;
- the impact of commuting on pilot fatigue, sleep, and circadian rhythms;
- commuting policies of commercial air carriers (including passenger and all-cargo air carriers), including pilot check-in requirements and sick leave and fatigue policies;
- postconference materials from the Federal Aviation Administration’s June 2008 symposium titled “Aviation Fatigue Management Symposium: Partnerships for Solutions”;
- Federal Aviation Administration and international policies and guidance regarding commuting; and
- to the extent possible, airline and pilot commuting practices.
Based on this review, the committee will:
- define “commuting” in the context of pilot alertness and fatigue;
- discuss the relationship between the available science on alertness, fatigue, sleep and circadian rhythms, cognitive and physiological performance, and safety;
- discuss the policy, economic, and regulatory issues that affect pilot commuting;
- discuss the commuting policies of commercial air carriers and to the extent possible, identify practices that are supported by the available research; and
- outline potential next steps, including to the extent possible, recommendations for regulatory or administrative actions, or further research, by the Federal Aviation Administration (FAA).
There is extensive research—including research specific to the aviation industry—on alertness, fatigue, sleep and circadian rhythms; cognitive and physiological performance; and safety. However, there is very little information specifically on pilot commuting, including commuting practices or airline policies and practices related to commuting. To help address this gap, the committee issued a call for input that was sent to pilot and airline associations and passenger groups and was posted on the project website: see Box 2. The people and groups involved were invited to respond to a series of questions specific to the types of information the committee was asked to review: see Box 3.
Organizations Contacted for Input
Pilot Associations and Unions
- Air Line Pilots Association
- Coalition of Airline Pilots Associations
- Allied Pilots Association (American Airlines pilots)
- Independent Pilots Association (UPS pilots)
- Southwest Airlines Pilots Association
- Teamsters Local 1224 (Horizon Air, Southern Air, ABX Air, Atlas Air, Polar Air Cargo, Atlas Worldwide, Kalitta Air, Cape Air, Miami Air, Gulfstream Air, Omni Air and USA 3000 pilots)
- US Airline Pilots Association (US Airways pilots)
- International Federation of Airline Pilots Association
- Air Transport Association
- Cargo Airline Association
- Federal Express
- National Air Carrier Association
- National Business Aviation Association
- National Air Transport Association
- Regional Air Cargo Carriers Association
- Regional Airline Association
- UPS Airlines
Groups That Represent Passenger Interests
- Air Travelers Association
- Flight Safety Foundation
In addition, the request for input was posted on the project website, http://www7.nationalacademies.org/bbcss/public_form_invitation.doc.
Topics Posed in Call for Public Input
Interested organizations or individuals were invited to provide comments on their perspective in the following areas, as relevant to their work and experience:
- (A) the prevalence of pilots commuting in the commercial air carrier industry, including the number and percentage of pilots who commute greater than two hours each way to work;
- (B) the characteristics of commuting by pilots, including distances traveled, time zones crossed, time spent, and methods used;
- (C) the impact of commuting on pilot fatigue;
- (D) whether, and if so how, the commuting policies and/or practices of commercial air carriers (including passenger and all-cargo air carriers), including pilot check-in requirements and sick leave and fatigue policies, ensure that pilots are fit to fly and maximize public safety;
- (E) whether, and if so how, pilot commuting practices ensure that they are fit to fly and maximize public safety;
- (F) how “commuting” should be defined in the context of the commercial air carrier industry; and
- (G) how FAA regulations related to commuting could or should be amended to ensure that pilots arrive for duty fit to fly and to maximize public safety.
This report reflects comments received to date; additional information received during the course of the committee’s work will be included in the final report. The committee also invited interested organizations and individuals to present their responses both in writing and in person at meetings held in November and December 2010 (see Appendix B for the public meeting agendas).
The committee also is assessing information from the following sources:
- a review of NTSB reports on aviation accidents to identify available information related to the contribution of commuting to flight crew fatigue;
- a review of confidential reports mentioning commuting and/or fatigue submitted to the Aviation Safety Reporting System (ASRS), a voluntary pilot reporting system funded by the FAA and hosted by NASA;
- a review of the comments related to commuting or fitness for duty submitted in response to the NPRM;
- a review of available information on relevant airline policies and practices in the international arena;
- analysis of data requested from airlines on pilot residence (approximated by zip code) and duty location (domicile or base) to enable an approximation of commuting distance and time; and
- a review of the relevant scientific literature.
For most people, commuting is a simple concept that represents the daily time spent traveling—almost always by ground transportation—from their homes to their workplaces. For pilots, the meaning of “commuting” is often more complex.
First, it is not uncommon for pilots to travel by air to and from their flight assignment. Commuting enables pilots to live a considerable distance from the airport at which they are based and travel to work in a relatively short time. For example, a two-hour commute via air would enable a pilot to live a considerably further distance than if the commute were by land. Second, commuting is not typically a daily occurrence, as pilot duty assignments often extend over several days and keep pilots away from home for multiple days at a time. As a result, a pilot’s commute to work may be undertaken as infrequently as once or twice per month—or more frequently, depending on the pilot’s flying schedule and commuting arrangements. Third, pilots sometimes travel to arrive nearby their domicile (the location of the base from which they fly) for a period before they are scheduled to fly, for logistical reasons, to have a rest opportunity, or for both reasons. Whether commuting time should be considered to start when pilots leave their homes or the place where they last slept is still under consideration by the committee. The key issue is whether a pilot begins the subsequent duty rested and fit to fly.
In addition to the lack of data on the prevalence of pilot commuting noted above, there are few data on specific methods or other characteristics of pilot commuting. Furthermore, all commutes, even commutes involving the same amount of time, may not have the same potential
to influence fatigue. Some commutes may not be cognitively or physically demanding (e.g., seated as a passenger on a train, bus, or plane), even to the point of permitting sleep to be obtained, while other commutes may entail more physical (e.g., standing) or cognitive (e.g., driving) demands.
For the purposes of this interim report, the committee is considering the following working operational definitions and issues in defining pilot commuting. These definitions and issues will be evaluated as the committee acquires more information, and they may be refined or changed in the final report.
The committee considers a pilot’s “domicile” to be the airport where a pilot begins and ends a duty period. This is distinguished from “hub,” which is a focus for the routing of aircraft and passengers. A pilot’s domicile may be at one of the airline’s hubs, but it may also be at an airport that does not serve as a hub for that airline.
The committee considers a pilot’s “home” to be the pilot’s residence: it is important to note that it is not necessarily the place where the pilot had the most recent opportunity for his or her customary sleep period. For example, the pilot may have access to a hotel room, apartment, or other sleep accommodation near his or her domicile.
The committee considers pilot “commuting” to be the period of time and the activity required of pilots from leaving “home” to arriving at the domicile (airport—in the crew room, dispatch room, or designated location at the airport) and from leaving the domicile back to “home.” Distinguishing a commute from a noncommute solely on the basis of the duration or distance of commute, or modality of commuting, will require closer examination and may be overly simplistic. Such an approach may be desired for operational applications, but the scientific foundations for establishing such a taxonomy relative to fatigue are not yet nearly as well founded as the scientific literature on fatigue in relation to time wake, time asleep, and time of day.
In its charge, the committee was asked to distinguish commutes of greater than 2 hours from other commutes. This dividing line, though potentially arbitrary,2 will be examined if the committee can obtain relevant data
Although it should be the cornerstone of the committee’s review, the committee has yet to uncover any systematic or comprehensive data3 on either the frequency of pilot commuting, the length of the commute, or the characteristics of commuting by pilots. The comments the committee has received to date from both pilots and airlines supports the view that pilot commuting is an integral and necessary aspect of the commercial aviation industry in the United States. A case could be made that the committee should ideally acquire systematic data to quantify the prevalence and characteristics of pilots and their commutes. However, developing, testing, implementing, and analyzing a pilot survey to acquire such data would require an
2The FAA’s recently published NPRM incorporates the suggestion that a “local area” be defined as an area within a two-hour travel period, regardless of mode of transportation.
3The only published information appears to be data included in the NTSB report following the Colgan Air crash, which reported that 68% of the Colgan pilots based at Newark were commuting, with the commutes being various distances (NTSB, 2010; pp. 47-48).
extended timeframe that well exceeds the time and resources available to the committee. Instead, the committee is relying on data it can obtain from the aviation sources (i.e., NTSB, ASRS, airlines, pilot associations) mentioned above. This effort is still in progress.
In addition to the general call for information, outlined in Box 3, the committee also requested information from individual Part 121 airlines, using a list of airlines provided by the FAA. Part 121 applies to most passenger and cargo airlines that fly transport-category aircraft with ten or more seats. Specifically, airlines were asked to provide data on pilots by domicile and home zip code: such data would enable the committee to obtain an individual-level approximation of commuting. The committee hopes to obtain data from multiple airlines, but very little information was available by the time of this interim report. Input to date, however, suggests that commuting more than 2 hours is not uncommon among pilots.
Characteristics of the aviation industry that influence pilot commuting include airline crew scheduling practices; airline route network and crew basing practices; and airline competitive and passenger demand factors that can cause pilot staffing requirements to change over time. These characteristics then interact with pilots’ preferences related to commuting and may influence their decisions about where to maintain residency. Certain airline policies and practices can facilitate or impede a pilot’s ability to commute, but at this point in the study, it is unclear how such policies potentially affect fatigue that may result from the commuting activity.
Airline Crew Scheduling: A Pilot’s Work Pattern
At most airlines, labor agreements between pilots and airlines establish specific policies and practices regarding flight crew scheduling (within requirements for flight and duty time as defined in Federal Aviation Regulations). Virtually all of these airlines rely on a bidding process to award monthly schedules (sometimes called lines or blocks) to pilots; selection advantages are given to pilots on the basis of seniority. Typically, a monthly schedule consists of multiple assignments of trips (sometimes called pairings), each of which may consist of several flights over a period lasting 1, 2, or up to more than 6 days. Each of these trips begins and ends at the pilot’s domicile (there also may be one or more overnights elsewhere) and thus comprises the basic duty assignment to and from which the pilot commutes.
While a “9 to 5” worker may commute on a daily basis, airline pilots may commute much less frequently while also remaining away from home for multiple days at a time on each of these trips. By federal regulations, airline pilots are limited to fly no more than 1,000 hours per year, or an average of about 83 hours per month. On the basis of this monthly limit, the number of flight hours per trip will determine the number of trips—and thus, potentially, the number of commutes—during the month. For example, if a pilot’s trips involve 20 hours of flying over 4 days, the pilot will do about four of these trips per month. There will be one or more days off between each trip. Other factors, such as flight cancellations and delays, have the potential to influence the length of a trip and the time off between assignments and, therefore, subsequent trips and commutes.
Using the seniority-based bidding process, pilots select the desired trips and days worked given their individual preferences, including the nature of their commutes, if any. For example,
a pilot who commutes a long distance by air to the domicile may bid for the monthly line of four, 4-day trips, specifically, trips beginning at the domicile late on the first day (allowing for the inbound commute) and ending back at the domicile relatively early on the fourth day (allowing for the homebound commute). This pilot will make four commutes during the month. In contrast, a pilot who lives near the domicile (e.g., driving 45 minutes to the airport) may bid for ten 1-day trips, each of which starts early in the morning and returns to the domicile later that day. This pilot will make ten commutes during the month. Note that the 1-day trips have more flying time per day, on average, and thus the pilot living near the domicile will work fewer days to accumulate the 80 flight hours for the month; the pilot with a long distance commute will have more work days and fewer days off to accumulate the same number of flight hours.
Airline Route Networks and Crew Basing
The point from which a pilot begins duty (at his or her base of operations, or domicile) is influenced by airline management practices that vary within the industry. For example, many scheduled airlines—those that operate on specific routes at scheduled times—operate a hub-and-spoke route network in which many flights converge on one airport (the hub) at about the same time so that passengers will have an opportunity to connect conveniently to a flight that is going to their ultimate destination (a spoke). Either a hub or a spoke city could be a pilot’s domicile.
Basing pilots at a hub can be attractive for airlines from the point of view of scheduling flexibility and for exchanging crews during connecting operations in the midst of an operating day. Even in a hub-and-spoke system, though, many airplanes are positioned at the spoke airport locations overnight, and basing pilots at a spoke airport can reduce the expenses of providing overnight accommodations (“overnighting”) for the pilots who work the originating and terminating flights of the day. In any case, the scheduling and routing of crews does not have to match that of the aircraft. For airlines using domicile basing, whether located at a hub, spoke, or elsewhere, the airlines typically leave the pilots responsible for performing the commute—by whatever modes and means necessary—so as to be at the domicile reliably on time and ready for duty.
In contrast to the practices of most major scheduled airlines, some airlines, often those offering mostly nonscheduled service,4 have crew-basing practices that reflect shared commuting responsibility among the company and pilots. These practices include home basing, in which the airline arranges a reserved seat on a flight from the pilot’s home to the city from which the pilot’s flight departs. Another practice is gateway basing, in which the airline arranges a flight (when necessary) from a specified gateway city to the departure city of the pilot’s first flight, and the pilot is responsible for the commute from home to the gateway city. For both home basing and gateway basing, a hotel may be provided to ensure a sleep opportunity prior to the first flight.
Competitive and External Factors
The evolving structure of the airline industry also affects the environment in which pilots make commuting decisions. Some airlines’ responses to a changing competitive environment have involved establishing new hubs and downsizing or closing existing hubs, as well as starting
4Nonscheduled airlines operate on customer demand without a regular schedule.
service to cities they previously did not serve or ending service to some cities. Airline mergers and acquisitions have also led to downsizing or elimination of hubs believed to be redundant in the post-merger route structure.
These sorts of changes may lead to domicile expansions, contractions, closings, or openings, with changes to where a pilot is domiciled. Changes to domiciles are handled, typically, through seniority-based bidding: pilots with relatively less seniority may sometimes be involuntarily moved to new domiciles in other parts of the United States (or even other parts of the world), or, in the extreme, furloughed from the company. Subsequently, recalls from furloughs in response to increases in travel demand may result in pilots being recalled to a domicile that is different from the domicile from which they were released. Seasonal scheduling causes other complications: it may result in changes in pilot domiciles in order to accommodate increased or decreased passenger demand for particular routes. In the absence of pilot commuting, these changes in the airline operating environment could lead to large-scale, sometimes short-term, relocations of pilots and families or inflexibility in the airlines’ ability to adjust to changes in staffing needs. The practice of pilot commuting thus enables airlines to adjust to these changes more readily, typically without incurring pilot relocation costs to a new domicile.
The practice of pilot commuting holds benefits not only for the airlines, but also for pilots. Pilots commute to some extent because they can and to some extent because they want to—how and how far a pilot chooses to commute depends on a host of personal and professional decisions involving family, economics, and logistics. Various combinations of work schedules, travel time, and ability to commute are feasible and, in the eyes of the person undertaking the commute, preferable to not commuting.
Pilots who have provided input for this study to date have told the committee that they commute because of both economic and life-style considerations. A pilot may choose a community of residence because of cost of living or tax advantage rather than living in his or her assigned domicile. A community may be selected based on such quality-of-life factors as a desired geographic region, proximity to a school system, or the existence of a support infrastructure for family while the pilot is on extended flight duty. Commuting also enables a pilot to maintain a stable residence if he or she is reassigned to another domicile.
Although any of the cities in a company’s hub-and-spoke network could be a given pilot’s domicile, there is no guarantee that the company will maintain a given hub-and-spoke pattern long enough for pilots to be assured that their choice for a permanent domicile will remain part of their company’s hub-and-spoke network. A point frequently made to the committee was that commuting can provide pilots and their families an aspect of certainty and control when facing the likelihood of mergers, domicile changes, furloughs, and the like, even when considering these as potential disruptions in the future.
Airline Policies and Practices Related to Commuting
Various airline policies and practices may facilitate or hinder commuting and affect pilots’ decisions regarding commuting. These include policies related to the consequences of failing to report to the domicile on time because of commuting, as well as those related to sick
leave and fatigue; the practices include the ease of commuting (e.g., being able to reserve a passenger seat or jump seat for the commute) and the opportunities for rest (e.g., in-base rest facilities). For the most part, policies directly related to commuting are unregulated and subject to collective bargaining agreements. The committee has requested information from airlines, airline associations, and pilot associations about these policies and practices.
Over the past several decades, the scientific knowledge base about the causes of fatigue and its effects on performance has grown significantly. The FAA-supported Aviation Fatigue Management Symposium: Partnerships for Solutions included several presentations summarizing the state of the science relevant to fatigue in aviation (and other transportation modes) (Federal Aviation Administration, 2008). Additional work was presented in the 2009 International Conference on Fatigue Management in Transportation Operations: a Framework for Progress (United States Department of Transportation, 2009).
It is clear that fatigue has multiple interactive sources. The primary ones that may be relevant to pilots’ commutes include duration of time awake prior to work, duration of time slept prior to work, restfulness of sleep (i.e., sleep continuity) prior to work, and the biological time (i.e., circadian phase) at which commuting occurs relative to the start of work. The duration of time at work (i.e., time on task) is a regulated factor for fatigue mitigation.
In the aviation industry, commutes that involve travel across multiple time zones have the potential to exacerbate the fatigue associated with commuting, as can chronic restriction of sleep for multiple days prior to commuting. It is important to recognize that these fatigue effects can be mitigated to some extent by following good sleep hygiene practices5 in the period between the end of the commute and the time of reporting for duty. It is unclear at this point, however, the extent to which such practices are followed by commuting pilots.
Extensive scientific evidence documents the multiple negative effects of fatigue on performance for tasks that are similar to those required to operate a commercial aircraft. These include adverse effects from fatigue on alertness and vigilant attention, on the speed and accuracy of performing tasks, on working memory, and on higher cognitive functions such as decision-making. The Institute of Medicine (IOM) defines fatigue as “an unsafe condition that can occur relative to the timing and duration of work and sleep opportunities” (Institute of Medicine, 2009, p. 218). It further states:
In healthy individuals, fatigue is a general term used to describe feelings of tiredness, reduced energy, and the increased effort needed to perform tasks effectively and avoid errors. It occurs as performance demands increase because of work intensity and work duration, but it is also a product of the quantity and quality of sleep and the time of day work occurs. (Institute of Medicine, 2009, p 218, drawing on Dinges ).
5Good sleep hygiene practices generally refer to those behaviors that effectively control all behavioral and environmental factors that precede sleep and may interfere with sleep, to ensure the sleep is as restful as possible, in order to promote daytime alertness, or help treat or avoid certain sleep disorders (Thorpy, 2011).
The extent to which commuting may contribute to pilot fatigue at work—by reducing sleep time, extending wake time prior to duty, or interrupting a habitual nocturnal sleep period—is not known. Moreover, pilot commuting practices and individual day-to-day experiences are characterized by tremendous variability.
Sleep and Circadian Rhythms
Further complicating an understanding of the relationship between commuting and pilot fatigue are inadequate data on the timing, duration, and quality of sleep before and during commutes. “Quality of sleep” encompasses factors that can affect the recuperative value of sleep, immediately prior to and during a commute period, such as noise, light, body posture, and ambient temperature.
Scientific understanding of sleep physiology is fundamental to the science of fatigue. Humans spend approximately one-third of their lives asleep. Circadian rhythms are daily rhythms in physiology and behavior that control the timing of the sleep/wake cycle and influence physical and cognitive performance, activity, food consumption, body temperature, heart rate, muscle tone, and some aspects of hormone secretion. When an individual remains awake into his or her habitual nocturnal sleep period, acute sleep loss (time awake extending beyond 16-18 hours) develops: it is characterized by a natural, physiological pressure to sleep (Institute of Medicine, 2009; Van Dongen and Dinges, 2005). This elevated homeostatic sleep drive in the human brain due to being awake too long creates a high pressure for sleep even during daytime work, increasing subjective fatigue and sleepiness while decreasing simple and complex attention and working memory, as well as other cognitive performance functions. These changes can result in adverse effects on performance that can be especially problematic when time awake while working is beyond 16 hours, when sleep prior to work is below 6 hours, and when work is being undertaken at a time when the body is biologically programmed to be asleep (i.e., an individual’s habitual nocturnal sleep period), which is most often between 10:00 p.m. and 7:00 a.m. (Basner and Dinges, 2009; Institute of Medicine, 2009; Van Dongen and Dinges, 2005).
Fatigue-related performance deficits from inadequate sleep can vary markedly across a day and while being awake at night (without sleep) because these two factors are not additive. Rather, sleep and circadian drives in the brain interact nonlinearly in the control of performance and alertness (Dijk et al., 1992; Goel et al., 2011). For example, during a 48-hour period of continuous wakefulness, there is a peak in poor performance after 24-28 hours of being awake (e.g., between 6:00 and 10:00 a.m. the following day). Subsequently, performance impairments from a night without sleep are actually somewhat less by 6:00-10:00 p.m. the following day (i.e., at 36-40 hours of being awake) relative to the peak for poor performance occurring earlier that morning (Goel et al., 2011). The detrimental effects of fatigue on performance may be exacerbated by a tendency for individuals to have reduced awareness of the cognitive performance deficits that result, even as these deficits increase in frequency with consecutive days of inadequate sleep (Van Dongen et al., 2003a).
Although the effects of acute sleep deprivation on performance may be influenced by many factors—often referred to as masking factors (Goel et al., 2011)—a recent meta-analysis of 70 articles that covered 147 cognitive tests of several moderators identified time awake as the most significant predictor of behavior during a period of acute sleep deprivation (Lim and Dinges, 2010). This finding could be especially relevant for pilots who get little to no sleep the
day before a flight and then undertake a lengthy duty day.
Much is known about the cognitive and functional deficits that result when healthy adult volunteers remain awake for 24-40 hours (Goel et al., 2009b; Harrison and Horne, 2000; Institute of Medicine, 2006, 2009; Philibert, 2005). That scientific understanding of the effects of sleep deprivation on cognitive functions has accumulated for more than a century (for reviews of this extensive literature see Dinges and Kribbs, 1991; Durmer and Dinges, 2005; Harrison and Horne, 2000; Institute of Medicine, 2009; Kleitman, 1963; Patrick and Gilbert, 1896). Additionally, recent advances in neuroimaging technologies have provided further insights into physiological changes in the brain and underlying performance functions that manifest themselves when fatigue results from reduced sleep (Bell-McGinty et al., 2004; Chee and Choo, 2004; Chee et al., 2006, 2008; Chuah et al., 2006; Drummond et al., 1999, 2000, 2005; Habeck et al., 2004; Institute of Medicine, 2009; Lim et al., 2007; Lim et al., 2010; Portas et al., 1998; Thomas et al., 2000; Wu et al., 2006).
It is now recognized that although most adults exposed to a night without sleep experience fatigue related declines in performance, the timing and severity of the declines vary across individuals, including pilots (Doran et al., 2001; Leproult et al., 2003; Van Dongen et al., 2004, Institute of Medicine, 2009). These differences in individual cognitive vulnerability to sleep loss may have a basis in genes regulating sleep and circadian rhythms (Institute of Medicien, 2009; Goel et al., 2009a, 2010). Persons with untreated sleep disorders are also subject to individual vulnerability and may experience negative effects on their performance and safety beyond those experienced by healthy individuals.
In addition to acute sleep deprivation, fatigue can be exacerbated by chronic partial sleep loss, also known as cumulative sleep debt, which occurs when the sleep obtained over multiple days is too short in duration to maintain behavioral alertness during the daytime (Van Dongen et al., 2003b). There is extensive scientific evidence that chronic undersleeping results in cumulative performance deficits across days and that the rate of the performance decline is inversely proportional to the sleep obtained (Belenky et al., 2003; Dinges et al., 1997; Van Dongen et al., 2003a). The performance deficits from chronic sleep restriction can also accumulate across days to levels equivalent to those found after one and even two nights without any sleep (Van Dongen et al., 2003a). Chronic sleep restriction that is followed by a night of little to no sleep results in severe deficits in cognitive performance (Banks et al., 2010). The threshold at which chronic sleep restriction appears to adversely affect performance in a majority of healthy adults is when time in bed for sleep is at 6 hours or less per 24 hours on a consistent basis. It is important to note that this threshold is the case for the vast majority of people who habitually need 7-8 hours sleep a night, but that the studies were not done on the minority of adults who are naturally short sleepers, requiring 6 or fewer hours per night. It appears that recovery from chronic sleep loss often requires extended periods of sleep (Banks et al., 2010; Belenky et al., 2003).
Since pilot commuting can involve sleep opportunities while seated or semirecumbent (e.g., in a car, bus, or plane), the recovery potential of such sleep becomes an important issue to understand in fatigue mitigation. For instance, both the angle of the back while sleeping and the characteristics of potential napping opportunities influence the overall restfulness of sleep. Sleeping in environments not conducive to sleep can result in reduced recovery potential, even during naps (Dinges et al., 1981). Sleeping in an upright position results in reduced sleep quality (i.e., less sleep time with increased awakenings) in comparison with sleeping in a lying flat or reclined position (Dinges et al., 1981; Nicholson and Stone, 1987).
Although napping has been shown to be an effective technique for restoring alertness and performance during periods of continued wakefulness, it is the timing and length of a nap, along with the timing of the nap in the circadian phase, that moderates the benefits of napping for performance (Bonnet, 1991; Caldwell et al. 2009; Dinges et al., 1987; Matsumoto and Harada, 1994; Rogers et al., 1989; Rosa, 1993; Vgontzas et al., 2007; Webb, 1987).
Recognition of the complex nature of the multiple interacting factors that influence the build up and reduction of fatigue as a state that can affect performance has been at the core of the development and application of various fatigue management strategies. The science of fatigue management has developed rapidly over the past decade in civilian transportation sectors, with much of the applied research sponsored originally by the military, where sustained and continuous operations pose acute fatigue-related challenges. There are now several well-documented candidate systems for measuring fatigue and its negative effects on performance. There are also mathematical models that demonstrate limited ability to predict fatigue using information on duty time and scheduling, sleep quantity and quality, circadian and time-zone information, and other variables.
There have been steady advances in various fatigue management technologies, including devices that monitor an operator’s level of alertness or performance, as well as devices that predict fatigue in advance of a work cycle or trip (Balkin et al., 2011). Although some of these technological approaches to fatigue management show considerable promise, there remain important unresolved questions and limitations regarding the validity and reliability of their use and acceptance by operators and industries (Balkin et al., 2011).
Among the most popular technologies for assisting in fatigue management are the mathematical models derived from research on the dynamics of performance relative to the interactions of sleep duration, wake duration, and circadian phase, which claim to predict performance during different work-rest schedules. A workshop sponsored by the U.S. Department of Defense, the U.S. Department of Transportation, and the National Aeronautics and Space Administration provided an opportunity to conduct an initial evaluation and comparison of seven of these mathematical models (Mallis et al., 2004). Although predictions of performance were promising, the evaluation showed that further research was needed to demonstrate the models’ validity and reliability using real-world data and that the models could not make reliable predictions of group performance risks from fatigue over multiday schedules (Dinges, 2004; Van Dongen, 2004). There is considerable research now under way to address how to use these measures, models, and other knowledge in the design and implementation of staffing and work-scheduling programs in order to minimize fatigue (see National Research Council, 2007). The potential for practical application of these models in the commercial aviation context—and particularly in relation to pilot commuting—is unclear at this time.
The issue of fatigue in safety-sensitive work operations cuts across many industries and has been addressed broadly in the scientific literature. The combination of work demands, sleep restriction, and circadian factors can negatively affect alertness, performance, speed, accuracy, and central nervous system functioning (Cabon et al., 1993; Goel et al, 2009b): see Box 4.
Factors in the Risk of Fatigue-Related Errors and Accidents
Risks of fatigue-related errors and accidents stem from multiple interrelated and interacting aspects of work, rest, and sleep. These include but are not limited to
- (1) duration of work periods within a single day and over time,
- (2) time of day at which work occurs,
- (3) variation in the timing of work within and between weeks,
- (4) duration of sleep obtained on work days and on non-work days,
- (5) frequency and duration of days off from work,
- (6) different vulnerabilities of workers to fatigue from these factors, and
- (7) volume and intensity of work.
SOURCE: Institute of Medicine (2009, pp. 218-219) citing the works of Dinges (1995), Drake et al., (2004), Folkard et al. (2005), Rosa (2001), and Van Dongen (2006).
Current federal flight duty time regulations (14 CFR 91 and 121) do not address pilot commuting. There is only a general requirement (in Part 91.13) that crew members should not be careless or reckless in the operation of an aircraft.
In response to P.L. 111-216 (the Airline Safety and Federal Aviation Administration Extension Act of 2010), the FAA’s current proposed regulation related to flight and duty time attempts to take advantage of the available research on fatigue, sleep, and circadian rhythms and, among other things, to consider the effects of commuting, means of commuting, and the length of the commute on fitness for duty. In these proposed regulations, time spent commuting is not considered duty time.
As noted above, as part of its effort to update these regulations the FAA issued an NPRM in September 2010 describing regulatory revisions in which commuting is included. The proposed regulations present commuting as fundamentally an issue of fitness for duty, defining a responsible commuter as a pilot who (U.S. Department of Transportation, 2010, NPRM, p. 55,874):
plans his or her commute to minimize its impact on his or her ability to get meaningful
rest shortly before flying, thus fulfilling the proposed requirement that he or she reports for an FDP [flight duty period] rested and prepared to perform his or her assigned duty.
In the NPRM (U.S. Department of Transportation, 2010 p. 55,875) the FAA states that “It is inappropriate to rely simply on the requirements to report ‘fit for duty’ in Part 91”6 and proposes a new Part 117 specific to fitness for duty. As a complement to issuance of the NPRM, the FAA issued a draft advisory circular (AC 120-FIT) on fitness for duty in which fitness for duty is considered as a joint responsibility of the air carrier and the crew member and outlines specific aspects of their responsibilities.
The NPRM has raised concerns about regulating commuting related both to infringement of personal choice and the possible inadvertent effect that would prompt “irresponsible commuting.” Hence, the proposed regulation points out that commute time should not be considered rest and that carriers have an obligation to “consider the commuting times required by individual flight crew members to ensure they can reach their home base while still receiving the required opportunity for rest.” It also conveys the FAA’s view that “irresponsible commuting” results primarily from a lack of pilot education regarding what activities are fatiguing and how to mitigate becoming fatigued. Pilot education is one of the specified objectives of the draft advisory circular on fitness-for-duty mentioned above. The effect of commuting on fatigue is also one element of a recommended training curriculum specified in the NPRM.
This committee has approached many international regulatory and safety oversight organizations, operators, and pilot associations—including the International Civil Aviation Organization (ICAO), International Air Transport Association, Flight Safety Foundation, and International Federation of Airline Pilots’ Association to obtain information regarding existing regulations, policies, and best practices regarding commuting outside the United States. In addition to regulatory approaches to fatigue, new developments both in the science of fatigue and performance and in management and regulatory philosophies have led to another approach in the transportation domain, usually termed fatigue risk management systems. These systems are focused on integrating scientific knowledge about fatigue and its management with the realities of airline operations. In essence, these systems recognize that responsibility for managing fatigue-related safety risks is a shared responsibility of regulatory authorities, operators, and individual pilots.
Fatigue risk management systems are currently under development by several airlines, and industry and professional groups, as well as national and international regulatory agencies, are involved in research and development efforts. The ICAO established a fatigue risk management systems task force to review scientific and operational knowledge and to develop detailed regulatory standards and guidance for member countries on implementation of such systems (see International Civil Aviation Organization, 2009). The proposed Standard and Recommended Practice was approved by the ICAO’s Air Navigation Committee on December 14, 2010; if it is approved by the ICAO’s council at its annual meeting in March 2011, it will be effective in July 2011.
P.L. 111-216 required U.S. airlines to submit to the FAA drafts of their Fatigue Risk Management Plans. Although these FRM Plans do not yet correspond to ICAO’s Standard and Recommended Practice, as part of its data gathering, the committee has requested information
6Part 91 does not specifically refer to “fitness for duty;” rather, as noted above it states that no person can operate the aircraft in a “careless and reckless manner.”
from U.S. airlines on whether their fatigue risk management plans take commuting into account and the committee will discuss the results in its final report.
The FAA approach is compatible with ICAO’s fatigue risk management systems initiative and the trend over the past two decades of many U.S. federal regulatory agencies to shift more responsibility to the organizations they regulate and to encourage cooperative rather than adversarial relationships. Generally, these initiatives rely on management systems using continuous monitoring to identify and mitigate potential risks before they have safety consequences Such voluntary FAA programs include the Aviation Safety Action Program and the Flight Operational Quality Assurance Program.
The Occupational Safety and Health Administration (OSHA) also has several voluntary compliance strategies that take a similar approach.7 (The Food and Drug Administration’s Hazard Analysis and Critical Control Points Program for food safety is another management systems approach. The success of such programs is a matter of some disagreement and, as noted by the U.S. Government Accountability Office (2004) in the case of OSHA, rigorous evaluation is needed to examine their effectiveness.
There are many issues that complicate consideration of whether and how commuting affects pilot fatigue in a manner detrimental to flight safety, not the least of which is the lack of comprehensive, industrywide data on the prevalence and characteristics of commuting. On the basis of the comments and documents the committee has reviewed to date, many airlines and pilots believe that pilot fatigue is a safety concern. However, the extent and circumstances under which commuting contributes to fatigue remain unclear. Airline policies and practices, characteristics of the aviation system, and individual pilot behavior all play a role in pilot fatigue. It seems to the committee that it is important to note that safety in scheduled air transportation has continued to improve over time, to the point where catastrophic, fatal accidents in such operations are statistically rare events. Although much remains to be done in the way of data collection and analysis, pilot commuting appears to be a fairly widespread aspect of these operations.
Over the next several months, the committee will follow up on its requests for information, continue to review relevant literature and information received, and attempt to analyze the role of the many factors involved in the issue of pilot commuting and fatigue. The committee’s final report, in keeping with the charge, will outline its thoughts on potential next steps, possibly including promising practices, recommended changes to FAA regulations, administrative actions, and research priorities.
7For details of OSHA’s cooperative programs, see http://www.osha.gov/dcsp/compliance_assistance/index_programs.html [January 2011].