Investigators don't yet know why Comair Flight 5191 ended up on the wrong runway just before it crashed early on Sunday morning. The government will check the flight crew's recent work schedules to see if they might have been addled by fatigue. According to Comair's president, the pilots had been "on a legal rest period far beyond what is required." How much sleep are pilots supposed to get?
Eight or nine hours, but it doesn't always work out that way. The Federal Aviation Administration has kept tabs on the work schedules of commercial pilots since at least the 1950s. In those days, major airlines couldn't keep their flight crews working for more than 30 hours in a week or 100 hours in a month. But there wasn't any well-defined limit on the amount of time they could work in a given day.
A series of plane crashes involving sleepy pilots led to a major revision of the rules in the 1980s. The FAA collaborated with NASA to study the impact of fatigue on aviation accidents. Flights crews that were pushed too hard seemed to have slower reflexes, become more easily confused, and suffer from visual illusions. They were also less likely to follow safety procedures.
The big change came in 1985. From then on, major airline pilots were required to have at least an eight-hour break between shifts on duty. As before, they could fly up to 30 hours per week, 100 hours per month, and 1,000 hours per year. Here's how the rule works: Every time a pilot completes a flight, you should be able to look back at the preceding 24 hours and find at least nine consecutive hours of off-duty rest time. (A provision in the rules allows a pilot's break to be shrunk by an hour one day—from a standard nine hours to eight—if he's given an extra hour the following day.) Pilots must also get at least one full day off every week.
Pilots complain about loopholes in the system. For example, a shift on-duty usually refers to the time a pilot spends going "block to block," or the period between pushing back at the gate in one airport and letting the passengers off at another. The government rules don't cover the rest of the time the crew might spend at the airport before and after a flight. (The airlines do work out more specific arrangements with their pilot unions.) A "rest period" might also include the time it takes to travel between the airport and a hotel, so an eight-hour break doesn't translate to eight hours of sleep.
The airlines and the pilot unions continue to bicker over the details. The 1985 revision came out of long negotiations between operators, employees, and the FAA—but that didn't stop the airline industry group from taking the FAA to court the day after the final rule came out. In the mid-1990s, the FAA proposed upping the break to 10 hours and adding another half-day to the mandated day off per week. No one could agree on the specifics of the new rule, and it was never made official.
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Explainer thanks Alison Duquette of the Federal Aviation Administration.