Defining and Measuring Aircraft Delay and Airport Capacity Thresholds (2014)

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2Average aircraft delay is often cited as an indication of airport capacity or used as a measure to support the asser- tion that new runways or other airport improvements are needed. Experienced airport planners may have successfully applied the concept of “acceptable delay” to help define air- port capacity for some time. Yet there is little guidance as to the amount of delay that defines capacity, thus the planner must justify the methodology used to estimate capacity for each project. The FAA’s National Plan of Integrated Airport Systems (NPIAS) and Airport Benefit-Cost Analysis Guid- ance provide some statements with delay numbers, but do not give definitive recommendations on how to determine capacity as a function of delay. In addition, the way flight delays are reported (as a function of scheduled flight/block time) often does not correlate well to a simulation model’s delay output (usually reported as additional time above “nom- inal” travel time). This leads to confusion about what “delay” really means and what delay thresholds should be used to determine capacity. Some clear guidelines on aircraft delay measures and airport capacity estimation are needed by the airport industry. Analyzing aircraft delays is complex—both when look- ing from a historical perspective as well as when estimating delays with forecast demand. There are challenges in analyzing what is an average delay: average annualized delay or average peak hour delay or average delay in a particular wind/weather condition for the average-day-peak-month flight demand? Another typical delay measure is the flight delay data reported by airlines to the Department of Transportation (U.S.DOT) and compiled by the Bureau of Transportation Statistics (BTS). These statistics generally are published by the media each month to compare the on-time performance of com- peting airlines. If using delay as a measure to define airport capacity, it is probably not practical to have one threshold that can be applied to all airports. When setting standards for delay thresholds, the metrics should work for benefit- cost analyses and environmental impacts. These metrics also should be applicable at airfield configurations that, due to their infrastructure, are able to accommodate greater levels of delay. There have been many historic and current disagree- ments between airports and airlines as to what level of delay is acceptable, balancing airports’ long-term demand accom- modation interests vs. airline cost and competition issues. It should be noted that not all delay is to be viewed negatively: a certain amount of delay is necessary if a system is to run efficiently when close to capacity. In conducting this research, the team interviewed more than 60 industry professionals from the FAA, airports, aca- demia, airlines, industry associations, as well as attorneys and airport capacity consultants/analysts regarding how they use/ analyze delays and their challenges in delay reporting. The discussions focused on issues related to airport planning. In addition, the team reviewed various planning reports from U.S. airports of all sizes to document the delay metrics and other criteria used to plan for airport development projects. This report summarizes and highlights key findings from the research to assist airport planners in their capacity/delay analyses. Different delay measures are used by various entities within the aviation industry. For analysts, delay is generally consid- ered as excess travel time—the difference between “actual” operating time minus a “nominal” or “scheduled” operating time. Yet, the simple word “delay” is used to describe many different situations. • Delay can either be a capacity indicator or an on-time per- formance indicator. When used to measure capacity, delay evaluates the effects of a specific flight demand as it oper- ates on the airfield resource. • Airline delay may occur before the flight leaves the gate, comparing “out” time or actual time of departure (ATD) with scheduled time of departure (STD). The gate delay could be an air traffic control (ATC)-required gate hold and also may be referred to as on-time performance. C H A P T E R 1 Introduction

3 • Tarmac delays, often are discussed as the “3-hour tarmac rule” that went into effect in 2010. – Excess taxi-out time between the gate and the runway may be due to runway capacity (departure queue delay), departure hold due to airspace constraint, or arrival air- port restricted acceptance rate and may or may not be weather related. – Excess taxi-in delay time between landing (“on” time) and gate arrival (“in” time) when gate is not available for arrival flight. • Some en route/airspace delay is accumulated before the flight is reported by FAA as delayed. Airspace delay can be composed of different ATC actions to achieve neces- sary aircraft separation—queuing, airborne hold, vector- ing, speed control—much of which is not obvious to the traveling public. Chapter 2 addresses aspects of airport delay that are most commonly encountered in airport planning. Information on operational delays and mathematical delay estimates are discussed from the perspectives of the various aspects of the industry. Chapter 2 also contains approaches and methods to calculating delay, including “how to” instructions for local air- port staff to analyze operational delays using FAA databases. Airport capacity analyses are described in Chapter 3, includ- ing metrics that have been used in various airport planning studies. The topics discussed in this chapter include defini- tions of airport capacity, a brief overview of approaches to cal- culating capacity, and capacity thresholds and guidance on the use of capacity metrics for different audiences. Readers should refer to ACRP Report 79: Evaluating Airfield Capacity for more detailed information on how to analyze airport capacity. Chapter 4 provides recommendations for using/applying delay and capacity analyses at an airport. Information is pro- vided on the relevance of particular delay and/or capacity mea- sures by airport type, airport characteristics, weather/capacity ratio, and project lifecycle phase. Rather than recommending threshold values, tables describe what actual operational flight delays may be experienced when specific average planning delays are applied. Using these tables, an analyst can establish appropriate delay thresholds for a particular airport. In conducting this research, various individuals in the industry suggested that the following additional delay met- rics may be needed: • Easily understandable by industry experts and lay people, • Communicates the “feel” for the impact of delays on the traveling public and tells the story that will resonate the benefit of new projects, and • Capable of use as a common measure at any airport. In this regard, suggestions also are presented in Chapter 5 for additional delay metrics that may better communicate the significance of the delay problem at particular airports. Chapter 5 also includes a discussion of future trends in capacity/ delay measures.