Two pilots flying a packed passenger jet admitted to falling asleep at the controls at the same time last month, according to ABC News.
The name of the airline was not released, but authorities say the incident happened aboard an Airbus A330 operated by a British-based airline.
An A330 is capable of carrying up to 350 passengers.
The pilots said they received little sleep over two nights because of a busy schedule. ABC News reports they planned to rotate taking 20-minute naps, but both fell asleep at the same time, leaving the jet on autopilot.
The U.K has rules that mandate the number of hours pilots need to sleep before they can operate an airplane, but in this situation, it was unclear how much sleep the pilots received due to changes in time zones and international flights.