The French Accident Investigation Bureau ruled out speculation that poor maintenance had contributed to the tragedy which killed all 109 people on board and four on the ground.

The plane burst into flames shortly after take-off from Paris' Charles de Gaulle airport on 25 July 2000.

A metal strip on the runway set in train the catastrophic chain of events. Debris from the puncture pierced the under-wing fuel tanks and started the fire that brought the plane down.

Following modifications to the supersonic airliner, British Airways has confirmed its fleet of Concorde aircraft should resume passenger flights in September. Air France says it hopes to resume its Concorde flights in October.

Last moments

According to the investigators, Concorde Flight AF4590 was cleared for take off on 25 July at 1642 local time (1442GMT) on runway 26 by controllers at Charles de Gaulle airport.

One minute and 13 seconds later, the control tower radioed to the crew: "(flight) 4590, you have flames, you have flames behind you."

The crew could do nothing to fight the devastating fire

The cockpit voice recorder reveals that the pilots detected a breakdown in engine number two beneath the left wing, which they then shut down.

Following this, the co-pilot is heard to say "warning, the airspeed indicator," and an unidentified voice in the control tower is then heard to say: "It's really burning and I'm not sure its coming from the engine."

The pilots then desperately tried to gain height, by increasing airspeed, to allow them to make an emergency landing at Le Bourget airport.

The voice recorder also reveals the crew were having problems with retracting the plane's undercarriage.

The control tower then cleared Concorde to make an emergency landing at nearby Le Bourget airport.

'Too late, no time'

However, as fire alarms and airspeed warnings sound in the background, pilot Christian Marty is heard to say: "Too late...no time."

Click here to see a full transcript of the last conversation between the crew and the control tower.

The crew continued their desperate efforts to reach Le Bourget, but as firefighters assembled on the ground, the last recorded words from the plane came from co-pilot Jean Marcot: "Negative, we're trying Le Bourget."

It has become clearer that this was a unique accident caused by a one-off chance of a piece of metal lying on the runway

Concorde crash preliminary report

Seconds later, the plane hit the ground near the town of Gonesse, ploughing through a small hotel.

In all, 109 passengers and crew were killed, together with four people on the ground.

The crew were unable to gain height or increase speed and could not retract the undercarriage.

This, the investigation says, followed the outbreak of a "substantial" fire under the left wing and problems with both engines one and two.

Concorde's unique wing design

Investigators say the plane's pilots had no hope of fighting or containing the blaze, and were right to have attempted to divert and make an emergency landing at Le Bourget.

Concorde has been grounded since the crash, but in mid-July 2001 it completed a successful supersonic test flight.

The British Airways fleet has undergone a �17m safety overhaul.

The plane's tyres have been reinforced and its fuel tanks covered with a protective liner to prevent a repeat of last year's accident.