Pilot fatigue poses a serious threat to operational safety, but understanding the nature of the problem and the times at which pilots are most at risk will facilitate operationally relevant fatigue-management strategies. This investigation sought to address these issues in a controlled investigation of the impact of sustained wakefulness on Air Force aviators. Ten current and qualified F-I 17 pilots completed the Multi-Attribute Task Battery (MATB), the Profile of Mood States (POMS), a resting eyes-open and eyes-closed EEG, and a standardized flight evaluation in an F-117 flight simulator at 5-hr intervals during the final 23 hours of a 37-hr period of continuous wakefulness. Results indicated significant decrements in mood, cognition, central nervous system activation, and flight skills began to occur in the predawn hours during a night without sleep. However, the most serious operationally relevant decrements appeared at approximately 0700 (after 25 hours without sleep) and persisted throughout the remainder of the deprivation period. The decrements suggested in the real world crew coordination likely will decline, information processing will become impaired, and a wide array of basic capabilities will be degraded as a result of compromised vigilance, poor situational awareness, and sluggish reaction time. Even the well-practiced flight skills of experienced pilots are clearly susceptible to the insidious effects of sleep loss. These quantified effects of untreated sleep deprivation will provide a baseline against which promising fatigue countermeasures can be assessed.
