Japanese investigators are probing an unusually long take-off run by a Polar Air Cargo Boeing 747-8F from Tokyo last month.
The aircraft became airborne just 85m from the end of runway 16L, according to Japan Transport Safety Board which has only just released details of the incident.
Runway 16L has a length of 2,500m (8,200ft).
The inquiry has not indicated whether the aircraft was conducting a full-length runway take-off or an intersection departure.
JTSB identifies the jet as N852GT, a five-year old 747-8F leased from Atlas Air. All 747-8Fs are powered by General Electric GEnx engines.
The aircraft, bound for Shanghai, had departed at 22:41, the inquiry says. Tokyo Narita has a restriction on night operations which comes into effect at 23:00.
Meteorological data for the airport at the time indicates good visibility and no adverse weather conditions.
Investigators have not indicated the circumstances of the prolonged departure roll, or given details of the take-off calculations performed beforehand.
Source: Cirium Dashboard
