An aircraft reported wind shear above Narita airport a few minutes before yesterday's fatal crash landing of a FedEx Boeing MD-11 freighter.
"About 4min before another aircraft captain told the control tower that wind shear occurred at 2,000ft above the runway," says an aircraft accident investigator at Japan's Aircraft and Railway Accidents Investigation Commission in Tokyo.
"The information was reported to the aircraft around the airport."
Yesterday's accident occurred at around 07:00 and footage taken at the time shows it was a clear and cloudless day.
But the investigator says the Japan Meteorological Agency has reported that just prior to the accident there was a northwesterly wind of 29kt (54km/h) with a maximum of 36kt and a minimum of 17kt.
He says the cockpit voice recorder (CVR) and flight data recorder (FDR) have been recovered.
Investigators from the US National Transportation Safety Board (NTSB) are due to arrive in Tokyo later today and Japanese investigators are due to meet with them this evening to discuss how to do the CVR and FDR analysis, he says.
"We will investigate all factors" including wind shear, says the investigator.
He also confirms the commission will "check other MD-11 accidents and speak to other aircraft accident investigating bodies".
Video footage of yesterday's accident shows the FedEx MD-11F crash landed on runway 34L, before bursting into flames and its wreckage coming to a rest upside down. The two pilots on board died.
There have been other accidents involving MD-11s that have crashed on landing.
In 1999, China Airlines MD-11 crashed on landing in strong winds at Hong Kong airport.
Also in 1997 a FedEx MD-11 freighter crash landed at Newark airport, New Jersey and burst into flames.