Passengers have described their terror after British Airways Flight BA2276 was engulfed in flames moments before take-off as it gathered speed on the runway of Las Vegas airport.

Passengers fled the aircraft after the pilot had brought it to a standstill after it had caught fire at McCarran International Airport in Nevada. Flames and black smoke consumed the undercarriage of the aircraft before firefighters brought the blaze under control.

Some of those on board said the preparations for take-off went normally and the plane was speeding along the runway, when a loud thud or explosion was heard.

"It all happened so quickly. I was jolted awake up by a huge thud. It took me a while to register what was going on. How long had I been asleep? Were we in the air? Were we still on the ground?" writes Guardian reporter Joshua Steinberg, who was aboard the flight.

He writes that passengers were initially told to remain seated, before they smelt burning.

"Our first move was towards the back of the plane. A flight attendant opened the door and had a look of utter panic on her face when smoke started to come into the plane. There were shouts to turn around and move towards the front. Some people looked chastened. There was a lot of smoke behind us and even the flight attendant was screaming at us to run."

Passengers then exited the plane from a door at the front, he writes.

"Once we reached the bottom, we ran. We didn't know where to go. We just ran. When we looked back and saw the other side of the plane the extent of the damage was clear." Some passengers described seeing windows melted by the intensity of the blaze.

Alex Crimmens, 29, was returning from holiday on the flight, which was scheduled to land at London's Gatwick Airport.

He told the Mirror that as the plane began to take off he heard a massive bang.

"People were understandably nervous, and then all of sudden I could hardly see out of my window because of all this smoke. We were travelling at the speed you'd expect a plane to be taking off at, so it was alarming."

As passengers evacuated the plane, he said there was increasing fear.

"Obviously people were worried, and in everyone's mind there's the fear that we've got a plane with smoke and flames and it's full of fuel -- we thought it could explode."

All 159 passengers on the plane and 13 crew members were able to get off the Boeing 777 safely. 14 people were taken to the Sunrise Hospital with minor injuries.

Aviation authorities delayed flights to the airport for up to two hours to stem the flow of air traffic, as the blackened aircraft blocked a runway.