In recent days, we have reported about the risks drones and lasers pose for air safety, but there may be an even bigger threat for travelers to be concerned with.

(AP Photo/Jacquelyn Martin)

A secret government study shows that air traffic controllers' work schedules often lead to chronic fatigue, which can compromise the safety of the entire air traffic system.

Federal Aviation Administration officials posted the study online Monday, hours after The Associated Press reported the findings.

The study was recommended by the National Transportation Safety Board to the FAA and the National Air Traffic Controllers Association to revise controller schedules to provide rest periods that are long enough "to obtain sufficient restorative sleep."

The findings of three-year-old study were both eye-opening and alarming.

Nearly 2 in 10 controllers had committed major errors in the previous year, including bringing planes too close together. Half of those cases were attributed to fatigue.

A third of controllers said they perceived fatigue to be a "high" or "extreme" safety risk.

Researchers found that workers they monitored slept an average of 5.8 hours per day during the work week. That number fell significantly when midnight shifts were involved.

The most tiring schedules required controllers to work five straight midnight shifts, or to work six days a week several weeks in a row, often with at least one midnight shift per week.

The study is composed of a survey of 3,268 controllers about their work schedules and sleep habits, and a field study that monitored the sleep and the mental alertness of more than 200 controllers at 30 air traffic facilities.

Schedules worked by 76 percent of controllers in the field study led to chronic fatigue, creating pressure to fall asleep.

The 270-page study made 17 recommendations to the FAA, including that the agency discontinue mandatory six-day schedules "as soon as possible."

FAA spokeswoman Laura Brown said they are taking steps to address the fatigue issue and allow longer breaks between shifts.

"Although fatigue is an issue in any 24/7 operation, the FAA has taken many positive steps to minimize fatigue," Brown said. "The fatigue modeling we've done shows that there is greater alertness using these updated scheduling practices."

However, the AP reports that controllers at several air traffic facilities said that six-day work weeks are still common.

The Associated Press contributed to this report.