Media reports made sleeping controllers seem like an all-too-frequent occurrence in 2011. In one widely reported instance, two airplanes landed at Washington Reagan International Airport without the requisite clearance after the controller on duty fell asleep. In another, a California-based regional controller helped an air ambulance land in Nevada after his local counterpart also nodded off. And then there was the case of a Tennessee controller who reportedly made a bed on the floor of the control room, complete with a blanket and pillows. “We're trying to get a hold of Knoxville approach or Knoxville departure,” one pilot said over the airwaves as he tried in vain to reach the sleeping controller.

In the aftermath, then-Transportation Secretary Ray Lahood sought to reassure the flying public that the skies were indeed safe.

These events were preceded by a National Aeronautics and Space Administration (NASA) study that assessed fatigue in the air traffic controller workforce. The study was motivated in part by a government recommendation calling for a revision of current scheduling practices that allow controllers to work five 8-hour shifts over 88 consecutive hours. In comparison, the average person will perform the same amount of work over 104 hours.

The schedule, commonly known as the rattler, is popular because it gives controllers three days off before they begin their next shift. It is also concerning because it provides a mere eight hours of relief between a day shift that ends at 2 p.m and a night shift that starts at 10 p.m.

The results of the NASA study were withheld from the public for years and repeated requests for access were declined. As current scheduling practices continued, they were also defended using the study’s (then unreleased) results as “evidence that working with proper rest periods produce less fatigue.” In the absence of data, those assertions could not be challenged. That is, until now.

This week, the NASA study was made public and the results are by all accounts troubling. A third of controllers surveyed perceive their fatigue levels to be “high” or “extreme.” Those working the rattler admit to being less alert at the beginning of their night shift and start work with a mere 3.1 hr. of sleep in hand. Controllers also find the rattler to be the shift where they are most likely to catch themselves “about to doze off” while working. These findings will undoubtedly fuel the narrative that controller fatigue threatens aviation safety. Yet, there is another cause for concern.

The study also finds that 66% of controllers who report having attention lapses while driving to and from work experience those lapses during the night phase of the rattler. About 28% of them report falling asleep at the wheel altogether. Why does this matter? According to a National Science Foundation poll, 42% of drowsy drivers admit to becoming more stressed, 32% acknowledge becoming more impatient, and 12% report driving faster than they should. More importantly, a study by the National Highway Traffic Safety Administration has found that 2.5% of fatal car crashes involve drowsy drivers and those crashes have resulted in over 5,021 deaths.

Simply put, the prospect of a drowsy controller sitting behind the wheel of car should be as unsettling as that of one sitting in front of a radar screen.

Controller fatigue is often viewed as worrisome for the traveling public alone. Sleepy controllers on the ground means less safety for passengers in the air. Such reasoning has thus far at least been the impetus for getting rid of the rattler. However, NASA‘s results demonstrate that the associated risk goes beyond the aircraft cabin. It may well affect the health and safety of controllers themselves.