Pilot was awake 24 hours before falling asleep at controls

A freight pilot who fell asleep at the controls on a flight to King Island and was unable to be reached by radio, had been awake for 24 hours.

The pilot, who was the only person on board, started to feel tired after leaving Devonport and quickly fell asleep while the plane was on autopilot, overshooting the destination by 78 kilometres.

The Piper PA-31 aircraft later landed without incident and the pilot then flew from King Island to Melbourne to complete his shift.

The Australian Transport Safety Bureau on Tuesday published a report into the flight on November 8 last year, finding the pilot had been awake for about 24 hours after being unable to sleep prior to take off.

The pilot's fatigue was at a level known to affect performance and even if the pilot had been able to sleep before the flight, he still would have been fatigued, the report said.

"This investigation highlights the need for pilots to assess their level of fatigue before and during their flight," the ATSB's Nat Nagy said.

"Before commencing night operations pilots are encouraged to modify their usual sleep routines to ensure they are adequately rested."