Two packed passenger aircraft collided at Heathrow airport last night as they taxied on a runway in preparation for take-off.
Witnesses reported scenes of panic on board the flights as passengers were evacuated after a British Airways Boeing 747 clipped the wing of a Sri Lankan Airlines Airbus A340, bound for the Maldives.
Although the London Fire Brigade said that nobody was injured in the incident, questions will once again be raised over safety procedures at the world's busiest airport.
Just three months ago two BA planes were involved in a similar collision, yards from the Terminal 4 building, when they ran into each other while one was reversing. Last night's incident occurred at 10.13pm. A spokesman for the British Airports Authority (BAA), said: "Heathrow Airport can confirm two aircraft were involved in an incident on the ground earlier this evening."
Sources for Sky News initially reported that an engine had fallen off one of the planes. But an airport spokesman later denied the claim, and said: "Absolutely false." He said those on board the flights were quickly calmed down.
He added: "Passengers were offloaded, they were put up in hotels and the flights were cancelled."
The fire brigade also disputed the initial television reports. "It was a minor collision between two planes who just clipped each other," said a spokesman. "There was no fire, no injuries, no damage."
Sky also reported that there were 40 fire engines in attendance at the scene, but last night the fire brigade said its vehicles had left.
In the incident in July, the left wing of a Boeing 777 carrying 200 passengers to Washington DC smashed into the tail-fin of an Airbus causing millions of pounds of damage. That collision was followed by criticism of safety levels at Heathrow, with BA staff quoted saying it was an "accident waiting to happen".
BA launched an inquiry that time, saying: "We are aware that two British Airways aircraft clipped one another as one pulled on to its stand on arrival at Heathrow and the other left its stand. Safety and security is paramount to British Airways and we would never compromise that."
At that time, a BA insider was quoted as saying: "The Airbus which had just arrived from Zurich was supposed to go straight to its parking stand. There was space. But the dispatcher who gives permission for it to proceed was not there. So it had to wait on the taxi-way.
"As it was waiting, the American-bound Boeing was pushed out of its stand in reverse. The reversing Boeing's left wing hit the back of the Airbus's tail. It's created a lot of damage. Some people were suggesting both planes had been written off."
The incident provoked sceptical analysis on an internet chat room for pilots, one of whom, who described himself as "Captain H. Peacock", wrote: "If the aircraft was struck from behind with the possibility of fuel lines and electrical cables connected to an operating APU (auxiliary Power unit then there is a risk of fire ... Nasty!"
Last month, BAA appointed Sir Nigel Rudd as its new chairman. Sir Nigel said "improving Heathrow" was his priority as it was "important to the nation".
Sir Nigel, deputy chairman of Barclays and a former chairman of Boots, said his new job was the "most challenging role I have ever undertaken".
British Airways was unavailable for comment.