2000). Maintenance of vigilance, particularly at night, is quite difficult. Pilots are expected to remain alert despite high levels of automation, low light levels on the flight deck, and regulations that require the pilots to remain in their seats for the duration of the flight unless their absence is necessary for the performance of duties in connection with the operation of the aircraft or biological needs, or if the crew member is taking a rest break and relief is provided. Getting up just to stretch or walk around is not allowed (Circadian Information, 2000; Neri et al., 2002). Non–24-hour duty/rest cycles, circadian desynchronization associated with transmeridian flights, and even time zone changes of only a few hours further compromise the pilot’s ability to remain alert (Mann, 1999).

Approximately 21 percent of the incidents reported to the National Aeronautics and Space Administration’s (NASA) Aviation Safety Reporting System (ASRS), a confidential self-reporting system for flight crews and others to report difficulties and incidents, are fatigue related (NTSB, 2002a). Data sets for both air carriers (Federal Aviation Regulations [FAR] 121) and commuter and corporate operations (FAR 91/135) contain numerous references to fatigue and difficulties maintaining vigilance (Aviation Safety Reporting System, 1998a,b). Fortunately, only one crash has been attributed to fatigue—that of American International Airways flight 808, which missed the runway at the U.S. Naval Air Station in Guantanamo Bay, Cuba, on August 18, 1993. According to the NTSB’s investigation, the probable causes of that accident included the following factors: impairment of the judgment, decision-making, and flying abilities of the captain and flight crew because of fatigue; the captain’s failure to properly assess the conditions for landing and maintaining vigilant situational awareness of the airplane while maneuvering onto final approach; his failure to prevent the loss of airspeed and avoid a stall; and his failure to execute immediate action to recover from a stall. Also mentioned in the report were the “inadequacy of the flight and duty time regulations applied to 14 C.F.R., Part 121, Supplemental Air Carrier, international operations and the circumstances that resulted in the extended flight/duty hours and the fatigue of the flight crew members” (NTSB, 1994b; Ranter and Luian, 2002).

John Meenan, Senior Vice President of the Air Transport Association of America, was technically correct when he told a House subcommittee that “there has never been a scheduled commercial airline accident attributed to pilot fatigue”(Meenan, 1999). However, several NTSB reports have played down or omitted the role of pilot fatigue even when the agency’s own investigators have considered it a significant factor (Circadian Information, 2000). For example, even though the NTSB report on a China Airlines Boeing 707 flight in February 1985 omitted any mention of crew fatigue, a later analysis of the accident by the Aviation Human Factors Team at NASA concluded that inattention caused by crew fatigue was a key



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