The pilot at the controls of an Indian jet that crashed this year, killing 158 passengers, had slept for more than half the flight and only drowsily rallied himself when it was time to land the plane, investigators have found.
At times his snoring was so heavy it was picked up by the in-flight recorders.
Serbian Zlatko Glusica had more than 10,200 hours of flying experience and his Indian co-pilot, HS Ahluwalia, had 3650. But as the Air India Express flight came into land at Mangalore Airport's notoriously short runway, the senior pilot was disoriented and his movements were slow as a result of "sleep inertia".
On the recorder, the co-pilot can be heard repeatedly warning him to abort the landing. The final words captured before the plane crashed were from one of the pilots: "Oh my God."
The investigation team has now submitted its report to the Civil Aviation Ministry, which will share the findings with the Indian Parliament.
But if reports citing the investigation's findings are correct, the panel's conclusions will add to growing concern about the dangers posed by exhausted pilots working long schedules.
Pilot unions are fighting efforts by struggling airlines, such as the Air India subsidiary, to get them to work longer hours.
In the past 15 years, up to 12 fatal crashes and numerous close calls have been blamed on pilot fatigue. Studies show exhaustion can impair a pilot's judgment in much the same way alcohol does and that it is not uncommon for fatigued pilots to focus on a conversation or a single chore and miss things around them.
In June 2008, an Air India flight to Mumbai missed its destination because the pilots were sleeping. When Mumbai air traffic controllers woke them, the plane and its 100 passengers were about 320km past the airport.
Pilot fatigue has been blamed for several fatal crashes, including one in 1997 when a Korean Air Boeing 747 heading to Guam ploughed into a hillside and killed 228 people.