Thank you, ma'am.
I do research in sleep and human performance. I work primarily now with the commercial airlines in the United States, specifically United Airlines. We study sleep and performance in what we call the operational environment, among pilots flying commercial flights.
As the gentleman just said, fatigue is fatigue; pilots are pilots. They are human beings, and they fatigue; it really is the same thing. The physiology, though, needs to be understood and used to support meaningful and useful regulations.
The sleep-related factors that affect performance are: time awake, an obvious one; time of day—there is the circadian rhythm in performance and alertness, with lowest performance and highest drowsiness and tendency to fall asleep occurring in the small hours of the morning, so time of day is important—and time on task, leading to acute fatigue relieved by time off task. These three things are common across humanity among fatigue issues.
In commercial aviation, flights can be scheduled at any time of the day or night, often with one flight then giving way, after a recovery period, to another, and so on. We have in the U.S. focused on regulatory schemes that are to a degree one-size-fits-all, but recently we've moved away from that and are looking not only at fixed regulations but at systems by which one could adapt and exist “outside the regulatory envelope”—this is the term we use.
This is called fatigue risk management. One establishes a preliminary safety case that a flight is safe, usually by using mathematical models or historical experience, depending upon where your interests lie. Once you've established in a preliminary way that it looks as though it will be all right, you then make measurements in flight of the active pilots, particularly at top of descent, when the most critical phases of flight typically occur. Once one demonstrates that there is equivalence in safety between “in compliance with the regulations” flights and the exception, the non-traditional flight, then one can fly that flight and do periodic data assessments to make sure one is safe.
Among critical things, in general in our measurements, the longer the flight the safer, because there is more sleep opportunity, and the more sleep people get.... We think in terms here of four-pilot crews with only two required in the cockpit at any given time during cruise.
Another critical thing is time of day. One should avoid, if one can, takeoffs and landings in the small hours of the morning, especially between 4 a.m. and 6 a.m.
There is one more thing, if you will indulge me. One very useful intervention in counteracting fatigue in four-person or in two- or three-pilot crews is whether in-flight cockpit napping is sanctioned. This was pioneered in the U.S. in studies at NASA but then not adopted because of what we call the Jay Leno effect: would they laugh? This is now done all over the world, except in the U.S.
I think this is good by way of introduction. I'd be happy to take comments and questions and join in discussion.