Seconds before the crash, the pilot of the Boeing 737-300, en route from Chicago to West Palm Beach, Florida, spoke to the control tower at Pittsburgh but did not report any difficulties.
Six-year-old Jason Moke, who was outside playing with a friend, said the plane 'went belly-up and then went down' into a wooded ravine, where it exploded.
The tail is the only reasonably large piece of the aircraft to survive the impact. 'This plane was decimated,' said Pennsylvania's Lieutenant Governor Mark Singel. 'The scene is one of absolute carnage. It's going to be difficult to remove the remains and identify the individuals.'
The plane came down in woods seven miles from Pittsburgh airport, which is newly modernised. 'All I saw was body parts hanging from the trees,' said Denise Goodich, a nurse who rushed to the crash site. 'There were people everywhere. You could just see parts of them.'
The crash is the biggest airline disaster in the US since 1987. It is also likely further to damage the safety reputation of USAir, 25 per cent owned by British Airways; its planes have been involved in five out of the last seven fatal crashes. The airline, the fifth largest American carrier, has 450 jets which make 2,500 flights a day, but has not made a profit since 1988.
Colin Marshall, the chairman of British Airways, said BA has no plans to withdraw from its partnership and did not believe USAir's crash record was a reflection of that company's financial difficulties. 'There is no thought of any change in our arrangements,' he said.
Mr Marshall said he believed there was no connection between the latest crash and the four USAir disasters that preceded it. 'It is much too early to speculate upon the circumstances of the (latest) accident,' he said. 'Each one has to be taken in isolation. And if there is no relationship between those accidents, then obviously it is the force of circumstance.'
Nobody knows why USAir has a worse record than other US airlines but the crash, at Aliquippa, Pennsylvania, is likely to affect future bookings. A spokesman said there was no connection between the crashes, adding: 'If there is something endemic, we will obviously fix it, but we are not aware of anything like that.'
The aircraft's cockpit flight recorder, which was recovered from the wreckage yesterday, should reveal to federal aviation investigators why the aircraft plunged into the ground out of a clear sky on a windless evening.
A USAir plane which crashed near Charlotte, North Carolina, in July, killing 37 of the 57 people on board, was trying to land in a severe thunderstorm. An earlier USAir crash during a snow storm at La Guardia airport in New York in 1992 was blamed on ice on the wings. And in February 1991, 34 passengers were killed in a USAir jetliner in Los Angeles. In September 1989, two died at La Guardia in a runway crash.
In a bid to gain access to American market - in the teeth of opposition from other US carriers who want USAir to go out of business - British Airways spent dollars 400m ( pounds 300m) to buy 24.6 per cent of the airline. But losses have continued to mount and BA has said it will make no further investments in USAir until the company is on the road to recovery. Bookings usually drop for a week after a crash, but passengers are more worried by accidents which have no obvious cause than they are by those which are the result of bad weather.Reuse content