TOKYO (AFP) - A FedEx cargo plane en route from China crashed in high winds and exploded in a ball of flames Monday at Tokyo's Narita International Airport, killing both pilots, officials said. The pair, both US citizens, were the only two people aboard the American parcel delivery company's wide-body McDonnell Douglas MD-11, which was flying in from Guangzhou in southern China. It was the first-ever fatal accident at Japan's biggest international airport and the country's first since 1996, when three people died in a Garuda Indonesia accident at Fukuoka airport. It was not immediately known what caused the crash, but the meteorological agency said strong gusts were blowing and that it had warned airlines of wind shear - a dangerous condition for planes coming in to land. "The plane was carrying packaged flammable liquid in its cargo," said an official at the Japan Transport Safety Board. It took firefighters using foam about two hours to extinguish the blaze, which completely destroyed the aircraft. Television footage showed FedEx Flight 80 touching down about 6:50 am (2150 GMT Sunday) and the aircraft's nose slamming into the runway before the plane sharply bounced onto its left wing. The jet exploded into a ball of flames and skidded at high speed while spewing a large plume of black smoke before flipping onto its left side and coming to a halt off the side of the runway. Fire engines and scores of emergency personnel in silver suits rushed to the gutted aircraft, which came to rest upside down with flames still shooting out of its fuselage, to douse the fire. The transport ministry identified the pilot as Kevin Kyle Mosley, 54, and the co-pilot as Anthony Stephen Pino, 49. It dispatched six accident investigators to the site. Airport traffic controllers had warned the pilots before landing of the possibility of wind shear up to an altitude of 600 metres (about 2,000 feet), the transport ministry said. Winds as strong as 72 kilometres (45 miles) per hour were registered around the airport at the time of the crash, the meteorological agency said. Akira Maene, an aviation analyst and former pilot at All Nippon Airways (ANA), told public broadcaster NHK: "It appears that the wind suddenly weakened and the plane lost aerodynamic lift." FedEx expressed its condolences for the victims and Masamichi Ujiie, its regional vice president, apologized for the accident. "We understand the airport's operation has been disrupted. We deeply apologize for the inconvenience caused," he told a brief press conference. The crash forced the closure of 4,000-metre Runway A, the longer of Narita's two runways, mainly used by medium and large aircraft. "We don't know when the runway could open again," said an airport spokeswoman who said more than 350 flights a day used the runway. The accident caused cancellations and delays, and scores of flights were diverted elsewhere, including Haneda airport closer to Tokyo. For Monday and Tuesday alone, Japan Airlines cancelled 58 flights and diverted 19, affecting some 16,700 passengers. ANA scrapped 17 flights and diverted eight, affecting at least 4,800 passengers. Late last month, 47 passengers and crew were injured when a Northwest Airlines Boeing 747 hit turbulence near Narita. Another air pocket hurt two crew over Japan in early March aboard an Air France Boeing 777.