As the 100 elated tourists took their seats, they couldn't have known they had 15 minutes to live. But aviation experts have known for 20 years that tyre blow-outs are a risk on `the world's safest plane'

By lunchtime the technicians in hangar QN had finished. With its engines popping and cracking as they cooled, Air France's oldest Concorde - registration code F-BTSC - sat gleaming under fluorescent lights. The team relaxed. Take-off was due at 2.25pm and the final tests had now been completed. It was 12.30pm.

It had been a tough morning. The plane had arrived from New York at 9.30 the previous evening with some kind of fault. Though the daily shuttle across the Atlantic had passed without incident, the chief engineer had recorded odd readings in his log book. The Concorde was towed to a maintenance bay where a 12-man team of technicians worked on the four Rolls-Royce Olympus 593 engines. At around 2pm the plane was towed to parking bay 2B, close to Air France's headquarters and next to the control tower.

Tuesday was not a good day for anyone at Charles de Gaulle airport. Storms had delayed scores of flights and angry passengers filled the departure halls. There were three-hour queues at the transfer desks and planes backing up all over Europe waiting for slots to land.

One of the delayed planes was the early afternoon flight from Frankfurt. It was carrying 96 Germans on the trip of a lifetime. They were flying to Paris where, courtesy of Deilmann luxury travel company, they were to board a specially chartered Concorde for their 3 hours 45 minutes flight to New York. From there a cruise liner, the MS Deutschland, would take them through the Caribbean.

The group landed in Paris shortly after 3pm. From the main terminals they were bussed to a smaller facility called T9, used by special charters. Again there were delays as their baggage was transferred. No one seemed to care, though. `They were all laughing and singing,' said an Air France official who checked the group in at T9. `They didn't mind waiting at all.'

Perhaps happiest of all was Klaus Frentzem, an eccentric 53-year-old secondary school teacher and Concorde fanatic who had saved for 20 years to fulfil his dream of a supersonic flight. He had brought some of his extensive collection of Concorde memorabilia with him and proudly showed it to others in the departure lounge. A few hundred yards away sat their plane in the muggy July heat. Two Air France technicians were tinkering with motor number 2. This time there seemed to be a problem with its `thrust reverser', the shields that are lowered over the jets' blast to slow the plane. The hydraulic pump which activates the reversers was not working, and though the technicians were full of assurances that the fault would not affect the plane's performance the pilot insisted it be replaced. No spare was available so a pump was taken from another Concorde.

The pilot was Christian Marty, one of the best known at Air France. With only 12 pilots qualified to fly the planes, all the Concorde crews were famous in the company, but 54-year-old Marty, with his shock of blond hair and outrageous achievements as a sportsman, stood out. A few years before he had completed the first crossing of the Atlantic on a sailboard. It had taken 37 days. He was a competition skier and a champion hang-glider too. `He was kind of intense,' said a friend. `He was a very dry, rigorous man.'

It was in character for him to insist on the change. `He would never fly unless everything was 100 per cent,' the friend, a Concorde co-pilot, said. `He was a perfectionist. That's one of the reasons he was such a great pilot.'

By 3.15 the pump had been replaced and Marty was satisfied. With co-pilot Jean Marcot, who had been flying Concordes for more than 10 years, and chief engineer, 58-year-old Gilles Jardinot, he started the pre-take-off checks. The six-strong cabin crew boarded the plane, and then the 100 passengers - including an American retired Air France employee who lived in Germany, an Austrian and two Danish tourists - filed up the mobile staircases and took their seats. It was 3.30. They had 15 minutes to live.

From his desk on the third floor of Air France headquarters, Jean-Cyril Spinetta, the chief executive, watched the Concorde taxi on to the runway. For more than 10 minutes the plane sat on the tarmac. At 3.42 Marty was cleared for take-off and at 3.44 began to accelerate down runway 26. Then flames appeared under the left wing. Spinetta saw them from his executive suite. Ground staff beside the runway saw them and alerted the emergency services. The control tower saw them and hit the red crash button to alert the whole airport. Within seconds, as amateur photographers fired off frame after frame and lounges full of delayed passengers watched aghast, the burst of orange lengthened into a 30-metre stream of fire and black smoke. Perhaps the only people who couldn't see the blaze were the crew of the burning plane.

But it is almost certain that they knew about it. Like all modern planes, Concorde has a range of systems to deal with fire in the engines. First a bell goes to warn the captain. He will usually shut off the noisy alarm and pull a fire handle on the ceiling of the cockpit above the windscreen to shut down the motor and cut off its fuel. A fire in one of Concorde's four engines should not cause too many problems. Three motors are enough to keep the plane airborne and allow the pilot, after dumping much of the 96 tonnes of aviation fuel, to look for an emergency landing site.

As the front wheels lifted off the ground at 3.44.56 secs, the control tower radioed Marty to tell him they could see flames shooting from the plane. `Number two engine is out,' he said drily.

But the plane was travelling at 250mph and had covered 4,200m of runway. It had reached V1 the speed at which it is considered impossible to abort a take-off safely. Though in hindsight it may have been a better option to take a risk, Marty followed the textbook procedure and pulled his stick back. The rear wheels left the ground. Flight AF 4590 was airborne. With a spout of flames and black smoke 40m long behind it.

Within seconds Marty called the tower again. He was now having trouble with a second engine and reported that his undercarriage would not retract.

Seconds later the pilot was on the radio again. He requested and was granted permission to try an emergency landing at Le Bourget airport, eight miles away, Spinetta watched the plane head south-west, leaving a thick line of oily smoke across the blue summer sky. It was only 100ft or so off the ground and had no thrust to gain altitude. Even that power was going. As the plane disappeared from view Spinetta quietly asked his secretary to get the Minister of Transport on the line. He had some bad news.

Marc Olivier, a 24-year-old basketball player, was practising with friends in a park near his home near Gonesse when he heard the scream of Concorde's engines. They stopped playing and looked for the plane. For most people in Gonesse - a small, blue-collar town ringed by dual carriageways and industrial estates- the twice-daily flypasts by the world's most famous passenger plane are hardly something to get excited about.

This time Concorde's approach sounded different. `You could hear the engines complaining as they tried to gain height,' Olivier told The Observer. `It was like they were screaming in pain.'

The basketball players watched as the plane started to bank to the left and lose height. Describing a huge arc, it was soon almost facing back the way it had come. Its nose came up until it was almost vertical. Flames continued to spurt from its underside. `It started turning as if to avoid the town and then began swinging around and almost seemed to stand on end,' Olivier said. `The left wing was hitting the tops of the trees. Then the wing hit the ground and the plane flipped over and slid along the ground upside down, and then there were two explosions and everything disappeared in smoke and fire.'

Marty, by design or accident, had avoided the main part of the town. The burning plane ploughed instead into a small hotel, the Hotelissimo, and exploded in a fireball `like an atomic bomb'.

Five people were killed instantly: two young Polish women on a work experience programme were resting in their rooms, and a young Algerian maid who had been taken on the day before was making up beds with Devrance Chundursing, a 42- year-old Mauritian mother of two. The fifth body was found on Friday in the rubble under an engine. It was so badly burnt that identification of the sex was impossible. No one knows who it is.

The death toll could have been much higher. A 21-year-old British student from Kent, Alice Brooking, was talking to her sister in London when the plane struck. She leapt through a first-floor window and suffered nothing more than minor burns and a bruised wrist.

A bus-load of 44 teenagers, members of a Suffolk youth band, had been delayed by traffic. Their late arrival meant hotel manageress MichÁele Ficheteau had given eight of her staff an extended break. Her secretary was out taking her dog for a walk. When the Concorde hit, the hotel eyewitnesses say it seemed to `vaporise'. Only a single charred wall remained upright. Within six minutes the emergency services were on the scene. There was little they could do other than play their hoses over the blazing wreckage. It was clear that no one could have survived in the plane. Early rumours of miraculous escapes were quickly proved optimistic. All 109 people on flight AF4590 died instantly. When the heat had subsided, rescue workers marked out the charred corpses and body parts with small plastic cones.

Passengers at the airport were informed that `major problems' had forced a temporary halt of all flights. As stunned Air France staff wandered through the packed halls, news of the disaster quickly spread. In terminal T9, where the passengers had whiled away their wait with songs and card games, airport staff were in tears . `I was crying and crying,' said Marie Segal, a shop assistant. `I had watched all these people having fun. I had sold them newspapers and books for the flight. One told me how flying on Concorde was his life's ambition. He was so excited.'

Yesterday investigators were still combing the jumbled wreckage for clues. The Air France Concorde fleet was still grounded. The press was still full of speculation.

Two main investigations into the crash have been launched by French authorities. One is run by the Bureau EnquÂetes-Accidents (BEA), the official government aviation investigations unit whose duty is to ensure such an accident never happens again. The other is a judicial inquiry which aims to find out who, if anyone, should be charged with `involuntary manslaughter', a serious criminal offence. Usually a single magistrate is in charge. This inquiry has three. The scale of the judicial probe demonstrates both the gravity of the potential charges and the importance of some of the players in the tragedy. Senior staff at Air France, at the airport, even the Minister for Transport himself, are potentially personally liable under French law.

There is a huge amount of data to work through. Just one of the two `black box' recorders contains 600 `parameters' which have to be analysed. Panels of experts including British, German and American specialists have been drafted in to help.

By the end of last week an explanation was beginning to emerge. On Friday investigators from the BEA announced that one, and perhaps two, of the four tyres on the undercarriage under the left wing had exploded as the plane was racing down the runway. Those who know Concorde's history were immediately reminded of an incident more than 20 years earlier. In 1979 two tyres exploded on an Air France Concorde as it took off from Washington's Dulles airport. Pieces of the wheels' magnesium rims and other debris were sent smashing into the plane's body.

A report by the American National Transport Safety Board, published two years later, revealed that `tyre debris and wheel shrapnel [had] resulted in damage to the No 2 engine, puncture of three fuel tanks, and severance of several hydraulic lines and electrical wires. Additionally, a large hole was torn in the top wing skin which covers the wheel well area.'

The plane returned safely to Dulles, but pilots have always remembered the incident. `They were lucky,' said Patrick Augin, vice-president of France's largest pilots' union. 'It did not cause a fire in 1979, but it could have. It's just a matter of where the holes are.'

As no debris from inside Flight AF4590's engines has been found on the runway investigators are playing down the idea that debris might have been sucked into the air intakes of its jets. Concorde is one of the few planes with air intakes situated directly behind its rear undercarriage. Experts point out that, with two huge intakes acting as giant hoovers, it is, whatever the BEA might say, unlikely that the motors themselves would have escaped unscathed.

Any debris inside the engines would cause massive and immediate damage, dislodging dozens of the sharp turbine blades used to compress air. The blades in turn would act like shrapnel inside the engine, smashing it apart and slicing through power and fuel lines. They would also be likely to puncture the fuel tanks held in the wing and cut their way into the twin engine alongside. Just because investigators haven't found any parts from the engine on the runway does not mean they were unscathed when the plane crashed. Another possibility is that a wheel jammed and then burst. The undercarriage would then smash on to the runway. The impact would force it back up into the body of the plane, rupturing fuel lines.

Once the thinly protected tanks in the wings or the fuel lines were damaged - by debris, or the undercarriage, or flying turbine blades- the leaking fluid would have been swiftly lit by a spark or chunk of hot metal. The burning fuel would be sprayed back by the airflow and the Rolls-Royce Olympus motors would have become huge flame-throwers. This would explain why, in the pictures of the stricken plane, the flames appear to originate from in front of the engines, though a plume of smoke and fire follows them. `Imagine a fireman's pressure hose squirting petrol across the mouth of a blast furnace and then multiply 100 or so times. It would have been so hot the metal of the plane itself would have been burning,' one former test pilot told The Observer. Another said the engines would have been converted into `giant cigarette lighters'.

Aviation experts appear to have been concerned about the potential for such a disaster for some time. In 1982 the US Transportation Safety Board recommended - after several more incidents involving malfunction of tyres on the plane - that Concorde should be allowed to land at American airports only after a full inspection of wheels, tyres and landing gear before every flight. Two subsequent incidents, more than a year apart, prompted a mild rebuke of Air France for the ineffectiveness of its earlier directives implementing these recommendations.

Pilots at British Airways, which operates seven Concordes, have long complained about the problem of burst tyres. With its fast take-off speed and sharp profile, Concorde is particularly hard on its undercarriage. On its first ever landing in America in 1976, engineers replaced a tyre which they felt was excessively worn. Some experts last week claimed that even a teaspoon left in its path could cause a blow-out. And the incidents appear to have recurred. At Heathrow in 1993 a burst tyre broke a glass-fibre water deflector and punctured a fuel tank. Earlier that year a tyre-burst due to brake seizure caused significant damage to a Concorde's engine, wing and hydraulics. The problem became so acute that BA installed a special alarm system in Concorde flight decks to alert the pilot on blow-out.

Ever since its launch, experts have also worried about the plane's susceptibility to fire. A report by American fire specialists Blazetech written nearly 25 years ago mentions the vulnerability of Concorde to fires produced by catastrophic engine failures. It also appears that a British Aerospace report in 1976 raised concerns over the fire risk in Concorde's fuel tanks.

A technical idiosyncrasy on Concorde explains why Marty was unaware of any blow-outs. When a tyre is faulty, a red light goes on in front of pilots - but only if Concorde is travelling at less than 150mph. At faster speeds it is impossible to stop, so the alarm is not activated. Marty had no idea what was happening underneath his plane. This explains why Marty attempted to raise the undercarriage - Air France's recommended procedure after a blow-out is to leave it down - after the plane took off.

Implicit in British Airways' decision to continue flying Concorde is the accusation that it was poor management or maintenance that was responsible for the Paris tragedy. BA still clearly believes that the blame is not with the craft itself. `We wouldn't operate the aircraft if we thought it was unsafe,' a spokesman said.

But the plane that crashed on Tuesday had undergone a 10-day inspection that ended on the Friday before the crash. And, with the rest of the Air France fleet, it had been given a complete refit, taking three months, last year. Nor can the company - still largely state-owned - be accused of cutting back on maintenance. Though costs have been slashed elsewhere to bring Air France into profit, Concorde has been seen as a symbol of national prestige and funded accordingly.

Air France is refusing to answer technical questions about the crash. It has yet to confirm that the undercarriage and tyres were properly inspected before take-off. Nor is it yet clear if the repairs to the plane's engines, and particularly the fitting of the cannibalised thrust reverser minutes before take-off, were a factor in the crash. There are also serious questions over the condition of the runway. Was there an undetected flaw that caused a blow-out? Or maybe a rogue piece of uncleared detritus from the scores of flights that use the strip each day? The two technicians who fitted the equipment and many of the ground staff who maintained the strip were undergoing psychiatric counselling last week.

BA's confidence in Concorde is not shared by Air France pilots. Some French unions said their members would refuse to serve on Concorde until the accident was explained. Etienne Lichtenburger, of the SPAC pilots' union, said: `No pilot will take up a Concorde until we have a clear account of what happened and what will be done about it.'

No one has blamed Marty. `He had to face the worst poss-ible scenario,' said Germain Chambost, a former Concorde pilot. `He did what he could, but there was no way out for him.'

Another Concorde pilot, answering questions from The Observer through an intermediary, said: `It could have been any of us. I am still in love with the plane, even if I don't want to fly right now. I keep thinking of him trying to keep control with two engines on fire. It could have been me. What was going through his mind in that minute? And what went through his mind when he knew he was going to die?'

Gonesse was quiet yesterday. On Friday the town had held a silent march to commemorate the dead. Some 2,000 locals, relatives of the victims and Air France staff walked down the high street, past the industrial estates, through the fields and out to the crash site. They were led by the mayor, Jean-Pierre Blazy, and Michéle Fricheteau, owner of the hotel. Blazy was angry in his grief, railing against British Airways' decision to keep their Concordes flying. Fricheteau just let the tears run down her face.

Five hundred metres from the wreckage they halted and hung their heads. Overhead the engines of a 747 roared through the sky.

Bottom of the safety league



Concorde's first fatal crash now puts the aircraft, statistically, at the bottom of the world safety league. The airliner had a superb 31-year crash-free record since its maiden flight in 1969 and entry into commercial service in 1976. Concorde's other incidents include:

1979 Air France plane has catastrophic tyre blow-out on take-off from Washington, damaging wing, fuel tank, engine. BA tyre blows out on take-off from Heathrow.

1989 Damage to BA plane's rudder in flight. 1991 BA plane's rudder breaks up at 56,000ft.

1993 BA plane's tyre blow-out at Heathrow causes fuel leak.

1994 Report reveals outer window panels crack at Mach 2. Safety checks ordered.

1998 BA plane turns back to Heathrow after panel falls off wing. Part of rudder falls off another BA aircraft in mid-flight.

February 2000 Engine failure as BA plane approaches Heathrow.

23 July 2000 BA and Air France report finding 2.5in cracks in the wings of all Concordes.