(CNN) -- The stakes were extremely high in this case of sleeping on the job.
A small freight plane overshot its Australian destination by nearly 30 miles because the pilot fell asleep in the cockpit, Australian Transport Safety Bureau (ATSB) said in a statement.
The pilot, who has not been named, flew the aircraft on November 8 from Tasmania to King Island, off the southwest coast of the country.
Flight tracking data from that day shows the Piper PA-31 plane, operated by Vortex Air, leaving Devonport Airport at 6:21 a.m. and passing over King Island before turning around. It landed on King Island at 7:21 a.m.
"During the cruise, the pilot, who was the only person on board, fell asleep, resulting in the aircraft overflying King Island by 46 km (28.6 miles)," ATSB said in a statement.
Authorities are now investigating the "serious incident" of "pilot incapacitation." It is unclear when the pilot woke up.
According to Vortex Air's website, it runs charter flights for "groups, corporates and leisure travelers to destinations around Australia."
It told CNN's affiliate Yahoo7 that it is investigating the "extremely rare occurrence" and said it was the pilot's first flight after returning from a period of leave.
Colin Tucker, the Managing Director of Vortex Air, said the company's pilot "unintentionally fell asleep while in command of the aircraft."
"The issue became apparent when Air Traffic Control was unable to contact the pilot in-flight, and the aircraft traveled past the intended destination point while operating on autopilot.
"The pilot safely landed the aircraft at King Island airport."
The charter company said it was the first scheduled flight for the day and subsequent flights were not affected.
The Piper PA-31 plane can cruise at a maximum speed of 270 mph and can carry up to 10 passengers, according to the aviation interest site Airlines.net.
ATSB said it will interview the pilot, review the operational procedures and release its investigation's report sometime at the beginning of 2019.
The Civil Aviation Safety Authority is conducting a separate investigation reviewing the fatigue management practices of the charter company, Yahoo7 reports.