Pilot Fatigue: Causes, Effects, and Aviation Safety Risks

Introduction: Pilot Fatigue as an Aviation Safety Threat

Because pilots are human, they are prone to the same physical limitations as everyone else — but the level of trust and responsibility assigned to them makes their performance far more critical to others. When pilots become tired, they are more likely to make mistakes or even to fall asleep, both of which are unacceptable for anyone seeking to pilot an aircraft safely. This paper examines how pilots are affected by fatigue in aviation and how fatigue can lead to accidents.

This analysis is important because, as Garland, Hopkin, and Wise (1999) emphasize, for pilots, "Fatigue is a proven killer" (p. 77). According to Deitz and Thoms (1991), "Fatigue, whether chronic or acute, can affect a pilot's ability to concentrate on the complex tasks associated with flying. Fatigue may be caused by emotional stress, lack of sleep, or poor physical health" (p. 8). In reality, however, the research shows that pilot fatigue can be caused by a number of other, less readily identifiable sources as well. A review of the peer-reviewed, scholarly, and popular literature on pilot fatigue follows, concluded by a summary of key findings.

According to Doyle (2002), fatigue typically manifests in three main forms: (a) sleepiness, which occurs naturally after people have been awake for about 16 hours; (b) physical fatigue, following periods of physical activity; and (c) mental fatigue, which follows prolonged effort on a demanding cognitive task. Moreover, many pilots today fly routes that last 16 hours or more (Fusco, 2000).

Forms and Frequency of Pilot Fatigue

A report from the Federal Aviation Administration found that pilots with 10 to 12-hour flight duty schedules were twice as likely to have an accident as those with fewer than 10 hours of duty; furthermore, pilots who worked 13 hours or more were almost six times more likely to be involved in a crash (Pilots' warning over long hours proposal, 2004). The importance of pilot fatigue to the traveling public was the subject of an essay by Tessier (1999), who reports, "Aviation is an industry that touches about 50 million travelers each year.... Yet few news organizations are doing regular reporting on safety issues. With crashes of commercial jets happening at a rate of about one each week worldwide, and air travel on course to double in about fifteen years, aviation is more than ever an important subject" (p. 29).

According to Peters (2000), the National Transportation Safety Board has ranked pilot fatigue among the top ten airline safety problems for more than a decade, and the FAA has rules intended to ensure that planes are not flown by exhausted crews; however, "those rules have never been enforced [by the FAA] since their inception" (Peters, 2000, p. 4).

When many people think of fatigue, the cause usually relates to simply becoming physically tired, but research quickly shows that pilots are subjected to a wide range of conditions unique to their profession (Doyle, 2002; Ward, 2004). For example, according to Garland and colleagues (1999), pilot experiences during World War II suggest that noise and vibration can contribute significantly to pilot fatigue. Likewise, Ward (2004) points out that pilots during World War II could become fatigued because of the very nature of their jobs and the aircraft involved:

Unique and Environmental Sources of Fatigue

"Once in the air and on course the flight would be comparatively uneventful, and the flight crew's job quite monotonous. Add to this the cold, the time of night, and the relentless drone of the engines and you have a recipe for disaster. Not unlike modern long-distance lorry [truck] drivers, there was a real danger of pilot fatigue" (Ward, 2004, p. 25).

During the latter half of the 20th century, newer and more sophisticated aircraft eliminated many of these sources of fatigue but introduced new ones in the process. For example, "The introduction of long-range, high-speed commercial jet aircraft has introduced the issue of the circadian rhythm phenomenon, or 'jet lag,' into concerns about pilot fatigue" (Garland et al., 1999, p. 315). This point is also made by Doyle (2002), who reports that "airline companies take pilot fatigue very seriously because they also have to contend with jet-lagged pilots" (p. 128).

The introduction of sophisticated aircraft, complete with vast arrays of displays and controls, can itself result in increased pilot fatigue. According to Mouloua and Parasuraman (1996), "Increasing task demands, such as increasing the number of displays that the pilot must monitor, also increases workload, particularly during demanding flight segments. Pilot fatigue also increases workload because it can reduce the capacity of the pilot to respond to task demands in a timely or appropriate manner" (p. 120). The authors provide a useful schematic illustrating how pilot skill, feedback, and system reliability interact to influence the level of fatigue experienced in real-world settings (Figure 1).

Conclusion: Ongoing Risks and the Need for Oversight

The research showed that pilot fatigue represents a real threat to the safety of the flying public, and the causes are numerous. Further, it would seem that whenever technological innovations are introduced to solve one type of pilot fatigue problem, they tend to introduce still others that may be unexpected and certainly unintended. Because pilots are people, they are subject to the same emotional and physical vulnerabilities as everyone else — but their level of responsibility for the lives of others makes these issues more severe, and the need for better oversight is abundantly clear.