Throughout the course of this outstanding research program, it has been evident that pilot fatigue is a significant safety issue in aviation. Rather than simply being a mental state that can be willed away or overcome through motivation or discipline, fatigue is rooted in physiological mechanisms related to sleep, sleep loss, and circadian rhythms. These mechanisms are at work in flight crews no less than others who need to remain vigilant despite long duty days, transmeridien travel, and working at night when the body is programmed for sleep.

Evidence regarding the existence and extent of fatigue in aviation has been gathered from several different sources and environments, including aviation operations, laboratory studies, high-fidelity simulations, and surveys. Studies have been consistent in showing that fatigue is an issue with complex, diverse causes and potentially critical consequences. Field studies specific to different aviation environments and using a range of measures (e.g., performance, physiology, and behavior) have revealed a number of factors related to fatigue. For example, in long-haul operations, the non-24-hr duty/rest cycles, the circadian desynchronization associated with transmeridien flights, and the sleep loss accompanying nighttime flying are all associated with fatigue (1). For short-haul operations, long duty days, sleep loss as a result of short nighttime layovers, and shortened sleep episodes due to progressively earlier report times across trips serve to create flight crew fatigue (2). In overnight cargo crews, even regular nighttime flying often results in incomplete circadian adaptation. Additionally, duty periods ending in the morning hours lead to sleep loss due to an increasing signal for wakefulness from the biological clock during this time. The problem is compounded by daytime layovers that can sometimes be too short for an adequate sleep opportunity (3).

Other evidence of fatigue has been obtained from flight crew surveys and researcher observations in the field (4, 5, 6). Flight crews routinely respond that fatigue is a concern, often admitting to having nodded off during a flight and/or arranging for one pilot to nap in the cockpit seat. The presence of fatigue has been acknowledged by flight crews for many years. Fatigue continues to show up in reports in NASA’s Aviation Safety Reporting System (ASRS), which we operate under FAA funding, as evidenced by recent ASRS database report sets for FAR 121 (7) and FAR 91/135 (8) operating environments.

Despite the widespread evidence that fatigue occurs frequently enough to be a significant aviation issue, it remains difficult to detect reliably and counteract effectively. Consequently, detection and countermeasures are two areas of active research by the Fatigue Countermeasures Program. For example, NASA researchers collaborated with NTSB investigators in assessing whether fatigue was present in the 1993 crash of a U.S. DC-8 freighter in Guantanamo Bay, Cuba. Three core physiological factors related to fatigue were identified (cumulative sleep loss, continuous hours of wakefulness, and circadian time of day). All three crewmembers were loaded on these fatigue factors. The NTSB implicated fatigue as a probable cause—the first time fatigue had been so identified in an aviation accident (9). This approach now represents a means of looking for the presence of fatigue in accidents or incidents across all transportation modes and other work environments as well.

A NASA/FAA countermeasure study empirically demonstrated the effectiveness of a planned cockpit rest period in improving performance and alertness in long-haul flight operations (6). Flight crews who were provided a planned 40-minute nap opportunity (resulting in an average of 26 minutes of sleep) subsequently exhibited improved physiological alertness and performance compared to flight crews not receiving the nap opportunity. The crewmembers napped one-at-a-time in a three-person cockpit with minimal disruption to normal flight operations and no reported or identified concerns regarding safety. The benefits of the nap were observed throughout the critical descent and landing phases of flight. The planned nap appeared to provide effective and acute relief from significant sleepiness experienced by crews in three-person nonaugmented flight operations. Following this study, the Fatigue Countermeasures Program submitted a draft advisory circular to the FAA in January 1993 on "Controlled Rest on the Flight Deck." Regulatory provisions that would sanction the appropriate use of planned cockpit rest remain under review. Several non-U.S. air carriers have already implemented the procedure.

Given that fatigue is a safety issue in aviation, the next logical question is how to address it. Unfortunately, there is no one simple solution. Fatigue is a problem with diverse causes, requiring a multi-faceted and comprehensive yet integrated approach. Based on current research, such an approach should have at least the following components: (a) education and training, (b) hours of service, (c) sound scheduling practices, (d) effective countermeasures, (e) incorporation of appropriate design and technologies, and (f) research (10).

Education and Training. Education establishes the knowledge base necessary for the successful implementation and acceptance of all other activities. Educational materials should include information on the physiological mechanisms underlying fatigue and what can be done to manage fatigue in operational settings. In 1994 the Fatigue Countermeasures Program, in collaboration with the FAA, developed an education and training module on alertness management in flight operations. The module is a 1-2 hour live presentation covering physiological mechanisms, misconceptions, and fatigue countermeasures. The presentation is supported by a NASA/FAA publication (11) that includes the presentation slides, explanatory text, and appendices on NASA studies, sleeping pills, sleep disorders, and additional reading. The module and publication are distributed to the aviation industry primarily through two-day train-the-trainer workshops held at NASA Ames Research Center. As of this date, 29 workshops have been held for 610 participants representing 234 different organizations from 17 countries. Our approach of training the trainers is having impact. A 1998 survey of participants indicated that the module is in use at 149 organizations reaching more than 116,000 flight crewmembers and others in the industry.

Hours of Service. Each operational environment should be encouraged to develop principles and guidelines for duty and rest scheduling that reflect the demands of that particular work setting. Appropriate guidelines will incorporate and reflect the latest scientific research on fatigue yet allow sufficient operational flexibility to meet often unique operational demands. In response to a request from the FAA for operational input, NASA assembled an international team of scientists and produced a principles and guidelines document based on the latest scientific information on fatigue (12). An advance version of this document served as one of several inputs to an FAA rule-making team that subsequently drafted a new flight/duty/rest regulation. The proposed rule was published for public comment in December 1995 with an extended comment period.

Scheduling Practices. Within the confines of regulated hours of service, there can remain significant leeway in the scheduling of flight crews. Sound scheduling practices should include scientific information about sleep, fatigue, and circadian rhythms, in addition to other factors, in creating and evaluating flight crew schedules. To foster and accelerate the development of models that can predict neurobehavioral functioning, the Fatigue Countermeasures Program recently co-sponsored (with the National Space Biomedical Research Institute and the Air Force Office of Scientific Research) a Workshop on Biomathematical Models of Circadian Rhythmicity, Sleep Regulation and Neurobehavioral Function in Humans. Organized by scientists from Harvard University and the University of Zurich, the workshop brought together basic and applied researchers from around the world to compare, integrate, and publish current models of circadian, sleep and human neurobehavioral systems.

Countermeasures. An integrated approach calls for making full use of personal, corporate, and even regulatory countermeasure strategies. These strategies can be implemented preventively, using them before duty and on layovers to reduce the effects of fatigue, sleep loss, and circadian disruption during flight operations. They can also be used operationally, employed in flight to maintain alertness and performance. The Fatigue Countermeasures Program has examined several strategies to counteract the effects of fatigue. In addition to the study on inflight cockpit napping, described above, it has conducted a study of the effectiveness of brief inflight activity breaks on alertness and performance (13). Flight crews receiving brief hourly activity breaks (involving mild physical activity and social interaction) showed improved physiological alertness for at least 15 minutes relative to a control group, while reporting significantly greater alertness for up to 25 minutes post-break. The effect of the breaks was especially pronounced during the portion of the flight when it is most difficult to remain vigilant—the early morning hours associated with the nadir in the circadian rhythm of body temperature.

Design and Technology. Technology continues to evolve rapidly, but humans have not changed their need for sleep, their rate of adjustment after circadian desynchronization, or the relationship between fatigue and performance. Good system design incorporates information about human physiology, its limitations and strengths, early in the process. Technological approaches that use this information can take many forms, including flight crew scheduling algorithms (i.e., the methodology of choosing flight crews) and alertness monitoring/management systems. Fatigue Program work in this area includes a project examining on-board crew rest facilities to determine the quantity and quality of sleep obtained and the factors that promote or reduce good sleep in the bunk (14). Onboard bunks are used in operations with extra (augmented) flight crewmembers onboard so that crews can rotate through flightdeck positions and non-flying crew can obtain sleep during long flights. A current NASA study is examining the feasibility of a video-based, automated, online system for drowsiness detection on the flight deck. Because we tend to underestimate our own degree of sleepiness, these systems have the potential to play a valuable role in detecting dangerous levels of fatigue and alerting crewmembers to their presence.

Research. Great strides have been made in the last fifty years with regard to knowledge about sleep, sleep need, the effects of sleep loss on performance, and related issues. Even more recently, major advances have occurred in human circadian rhythms research, leading to an improved understanding of these daily rhythms and their control by the human circadian pacemaker in the brain. However, more research is needed to fully understand the capabilities and limitations of the human sleep and circadian systems. An additional challenge is the appropriate application of this research to operational environments such as aviation. Given the recent development of technologies claiming to be able to detect fatigue, focussed research is needed to ascertain the sensitivity, reliability, and validity of these devices (15). Research also needs to continue to address regulatory, scheduling, and countermeasure questions. The area of fatigue is plagued by misconceptions about its causes and characteristics. There is no substitute for valid empirical data to guide decision making and policy.

It should be evident that no single approach or "fix" can eliminate fatigue as an issue from aviation and other around-the-clock operations. A successful approach will attempt to maximize each individual component, resulting in an effective overall program. Measures taken to address fatigue must also allow for needed operational flexibility. Clearly, fatigue-related issues cannot be the only ones considered in regulating hours of service, developing scheduling practices, creating new technologies, etc. However, they need to be included. When scientifically based data on fatigue, its causes, and its consequences are considered along with economic, regulatory, operational, and other factors, safety in aviation can be measurably improved.

Mr. Chairman and Members of the Subcommittee, that concludes my formal testimony. I would be pleased to respond to your questions.