There have been a number of stories in the news recently about US air traffic controllers falling asleep on the job. There has been one example of an obvious violation of rules, but overall I wonder about the systemic failures that have caused the problems.
An article in The Wall Street Journal by Langhorne Bond and Robert W Poole Jr discuss the causes.
Apparently the Federal Aviation Authority (FAA) has known about Controller fatigue for decades but "has repeatedly swept it under the rug." One of the likely problems is the shift pattern. One of the most popular is called 2-2-1: Controllers work two swing shifts, two day shifts, and one midnight shift. The second day shifts ends at 2 p.m. and the subsequent midnight shift begins at 10 p.m., just eight hours later. Such a schedule disrupts circadian rhythms, creating fatigue on the midnight shift. Controllers and their union have fought to keep 2-2-1 because it gives them a three-day weekend afterwards.
The National Transportation Safety Board (NTSB) has called for abolishing 2-2-1 and the inspector general for the Department of Transportation has called for a 10-hour minimum between shifts in general, and 16 hours after a midnight shift.
The other cause of fatigue on midnight shifts is black backgrounds on controller display screens, which require dark rooms for best visibility. But dark rooms tend to induce drowsiness, especially on a midnight shift. It is now common international practice to have light gray background screen displays that can be used in high-light environments, but in the U.S. this has been ignored.