Sleeping on the job is a fast way to get fired – especially if it’s one that takes place at 30,000 feet above ground.

That’s the reality that two British pilots confessed to. According to a report by the U.K.’s Civil Aviation Authority (CAA), two pilots nodded off while operating an Airbus A330, the Guardian reports.

But the pair reportedly won’t receive serious disciplinary action after they admitted to the incident that took place on Aug. 13, soon after the 325-seat plane took off. The pilots, who had slept a total of five hours the previous two nights, said they agreed to take turns sleeping while leaving the aircraft on autopilot. After one of them woke up to see that they had both been asleep at the same time, they decided to report the incident that the plane was being flown unsupervised.

"The plane is capable of cruising on autopilot, but if there's an emergency there would be no one to take the controls,” David Learmount, an air safety expert, told The Sun. “The pilots need to be alert. But the greatest danger is they wake up and do something as a knee-jerk reaction while still suffering sleep inertia."

While CAA did not disclose which airline the pilots worked for, Virgin Atlantic, Thomas Cook Airlines and Monarch Airways each have A330 aircrafts in their fleets.

"This was a serious incident but an isolated one. I think lessons will be learned from this. We are circulating this report within the industry,” a CAA spokesman said. "We don't know why the pilots had had so little sleep before this flight. They were taking it in turn to have rest periods, with the one always checking the autopilot and it looks as if both fell asleep at the same time."

This isn’t the first time tired pilots have taken a snooze in the cockpit. In March, an Air New Zealand pilot fell asleep during a flight between London and Los Angeles, the BBC reports.

"During the cruise phase of the flight one of the two operating pilots nodded off twice for around a minute and woke spontaneously," Air New Zealand said in a statement. "The other operating pilot on the flight deck was aware of this and safety was not compromised at any point."

In the United States there have been several reported incidents of pilots overshooting the runway or spending more time in the air after pilots fell asleep. According to the National Transportation Safety Board (NTSB), undiagnosed sleep apnea might be the cause. The respiratory condition where a person takes one or more pauses in breathing during sleep, can cause fatigue.

"They feel tired and sleepy when they wake up in the morning," Dr. Vahid Mohsenin, director of the Yale Center for Sleep Medicine at Yale University, told Time Magazine. "I've seen a lot of patients that had several car crashes before they were diagnosed. They were related to sleepiness at the wheel."