Air crash investigators will focus on what caused an apparent total loss of power in the final minute of the flight from Beijing.

The Air Accidents Investigation Branch will publish an initial report into the crash within 48 hours and may make immediate safety recommendations to both Boeing and BA.

Air crashes are almost always caused by a combination of circumstances. Even when a technical failure is found to be the key factor human error usually plays a part in turning a problem into a full-scale emergency.

Yesterday’s was the most serious crash in the 12-year history of the Boeing 777. No passengers or crew have been killed on that model of aircraft, even though more than 670 are in service around the world.

The aircraft that crashed was only six years old and was one of 43 in BA’s fleet, which may have to be withdrawn for checks in the next few days.

Investigators will try to determine why both engines appeared to have failed, leaving the pilots without enough power to make it to the runway. They landed just inside the perimeter fence, more than half a mile from the usual touchdown zone.

Twin-engine aircraft occasionally lose one engine but can continue safely and land normally on the other.

A BA pilot said that possible causes were a lack of fuel or a fuel-pump problem. Engines are sometimes destroyed on approach by birds flying into them, but this usually causes a loud bang and no passenger reported hearing that.

David Learmount, safety editor of Flight International magazine, said: “There appears to have been a massive reduction in power at a very late stage. The pilots had no time to warn anyone and all their focus was on getting the plane down. They seem to have been going very slowly and were extremely lucky that they made it over the perimeter fence.”

An airport worker told the BBC that the pilot had said that he had lost all power and cockpit electronics, and had been forced to glide into land.

Others spoke of seeing the Boeing coming in at a very low level and banking heavily. “It was so low you would think you could lean out the window and touch it,” said one.

David King, Chief Inspector of Air Accidents, said last night that an initial report would be issued within 48 hours but that it could take some time to discover the cause.

Mr King said: “At present, my staff are involved in preliminary inquiries to establish the known facts of the accident. I will release an initial report within 48 hours. The cause(s) of the accident can take some time to establish but I will also release a preliminary report within 30 days.

“The final report may take considerably longer to produce but I also have a duty to take any action we consider necessary as soon as we become aware of any safety-related aspects arising from the investigation.”

Robin Tydeman, who was an RAF pilot and a commercial pilot during his flying career and has been examining air accidents for ten years, has been appointed as the investigator in charge.

He was involved in the development of the first flight simulators for the Boeing 777, the model of plane involved in yesterday’s accident.

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