Pilots fell asleep while flying at 30,000 feet while in the cockpit of a 300-passenger plane that was traveling to Britain last August, according to U.K. aviation authorities that spoke to CNN.

The incident on the Airbus A330 occurred while the plane was operating on autopilot on a long-distance flight. The U.K. Civil Aviation Authority (CAA) didn't reveal any other details about the flight, such as the airline, the route or the destination airport.

The incident was a result of bad scheduling by the airline, Richard Taylor, the spokesman, said. The pilots were only able to get five hours of sleep over two nights "due to longer duty period with insufficient opportunity to sleep," the report states. "Both crew rested for 20 minute rotations and fell asleep."

The airline arrived safely at its destination. It was also the first incident of that type to occur in two years, according to Taylor. It's unlikely the pilots will be disciplined.

Fatigue is one of the highest ranked problems in the pilot community, according to CNN. Rules that surround sleep and relief crews vary from country to country.

It's "far too complacent about the levels of tiredness among British pilots and failing to acknowledge the scale of the underreported problem," Jim McAusian, the general secretary of the British Pilots Association, said. He used the example to bring up pilot fatigue as an issue that should be addressed by the CAA.

The European Parliament is expected to vote on new EU rules that regulate flying hours next week. The proposed rules will increase "tiredness among pilots and the risk of dangerous incidents," McAusian said.

In the U.S., flights that are longer than eight hours require a relief pilot to be on board to take over so pilots can take a break to sleep. For flights that will be longer than 12 hours, an additional relief pilot must also be added.