As the jet flew through the dead of night, most passengers slept. They included a mother and her five-year-old son, and an 11-year-old boy returning to his boarding school in Bristol.
Alexander Bjoroy had spent an idyllic half-term break with his expatriate family in Brazil. His parents, Robin and Jane, had seen him safely to the airport, then waved him off as he returned to Bristol's £5,970-a-term Clifton College.
One couple on the flight, a young doctor and lawyer, had married only the day before. After a wedding reception in a Rio nightclub, they had boarded the plane to begin their honeymoon.
Crash site: Recovery crew members preparing to tow a part of the wreckage of a Air Bus A330-200 jetliner which crashed in June 8, 2009
It was June 1, 2009, and this was Air France Flight 447 from Rio de Janeiro to Paris - a routine international flight.
In the early hours of that fateful morning, however, something dreadful occurred. Air France Flight 447 made its final radio transmission - and then all contact was lost.
The flight simply vanished. On the ground, French officials told desperate relatives: 'We wait, we pray, we will know more this afternoon.'
So began one of the most catastrophic and troubling air disasters of modern times, a crash that killed 228 people from 32 nations. Five Britons, including 11-year-old Alexander, died.
Distraught: Friends and relatives of flight 447 passengers comfort each other after a mass in their homage at the Candelaria Cathedral on June 4, 2009 in Rio de Janeiro
Fernando Schnabl was waiting for his wife, Christine, and their little son Philipe to land. Travelling separately in order to use up their Airmiles, he had kissed his wife goodbye in Rio de Janiero and then boarded a different plane to Paris with Celine, their three-year-old daughter.
Landing at Charles de Gaulle Airport in Paris the next morning, Fernando was looking forward to seeing his wife and small son again.
But, as his plane taxied towards its stand, a passenger in the next seat switched on his mobile phone and said that a flight from Rio was missing.
'Then he said it was Air France and I was very scared, ' says Fernando.
'And when the crew called my name, I knew something really bad had happened. The way they treated me with so much concern, but not wanting to tell me anything, left me with no hope at all.'
Continuing search: Despite an exhaustive search, costing millions, the black box recorders of the Air France jet have not been recovered
Staff led Fernando and his daughter to an airport lounge, where other distraught relatives were gathering.
Alexander Bjoroy's family learned of the crash at their home in Brazil, and broke the painful news to his younger sister, Charlotte. What had happened to their treasured child?
Hampering the search was the fact that no one knew the precise spot where the jet had disappeared. It had left Brazilian airspace, but had not radioed its next position.
In the hours and days after the crash, officials at Air France began to study a series of error messages sent by the plane's automatic communications system via satellite, which indicated that it had experienced 'multiple technical failures' in its last minutes in the air.
Airbus A330-200: A new documentary claims that technical failures with air speed indicators might have led to the crash
What had gone wrong? An awful five days later, the shattered wreckage of Flight 447 was discovered, floating in the Atlantic 750 miles off the coast of Brazil. All 228 passengers and crew were dead.
Despite a £24 million search operation, the all-important black boxes could not be recovered.
No one was able to explain what had happened. To the anger of relatives, French investigators will not make a final report on the disaster until the black boxes are found.
But now, for the first time, the story behind this devastating air disaster can be told. A BBC2 documentary, Lost: The Mystery Of Flight 447, to be screened tomorrow night, has brought together leading aviation experts to conduct a forensic investigation into the crash.
Amazingly, they have been able to pinpoint exactly what happened on that fateful night, even though the aircraft left barely a trace when it crashed.
Furthermore, they are able to answer the question: could it happen again?
Tony Cable worked for the UK Air Accidents Investigation Branch for 32 years. He was the senior investigator on the fatal Concorde crash in Paris ten years ago, and on the Lockerbie bombing.
'The normal way of investigating an accident is to look at the crash site. In this case, though, there's only a small amount of floating wreckage,' he says.
'The flight data and cockpit voice recorders are clearly at the bottom of the ocean with the rest of the wreckage - a very, very big handicap to the investigation.'
How, then, did the team begin? First, they eliminated the possibility of a terrorist attack.
'The possibilities that immediately come to mind would be a bomb or a structural break-up,' says Cable.
He drafted in John Cox, one of the world's leading aviation safety consultants, and they pieced together the recovered aircraft parts to find out what forces acted on them in the last moments of flight.
This method was used to solve the mystery of TWA flight 800, which crashed off the coast of New York in 1996. By examining fragments of that fuselage, experts determined that faulty wiring had caused a fuel explosion.
Engineer Jim Wildey is a veteran of that investigation. Looking at the recovered parts from Flight 447, he made the first major breakthrough: the plane showed signs of a highspeed impact with the water.
'The nose cone has been flattened, crushed and torn,' he says. 'This is a very clear sign that this piece was on the airplane when it hit the water.'
A floor section from the cargo compartment also revealed that the plane was level at the point of impact, and hit the water at speed.
It appears, then, that flight 447 didn't explode in mid-air; it simply fell out of the sky. But if there was no explosion, what did happen?
The A330 is a jewel in the crown of European aerospace giant, Airbus. It had previously been considered extremely safe, with 700 in service around the world and not a single passenger fatality before Flight 447.
The plane uses a state-of-the-art fly-by-wire computerised control system, where mechanical levers are replaced by electronics. When the autopilot is switched on, the plane flies itself.
'Ninety-nine per cent of the time when you're sitting as a passenger flying at 35,000 feet, the autopilot is flying the aeroplane,' says Captain Martin Alder, former chairman of the British Airline Pilots' Flights Safety Group.
Using Air Traffic Control transcripts, Cable has been able to piece together the last devastating moments in the cockpit.
He believes that flight 447 would have been on autopilot as it headed out over the Atlantic, with Captain Marc Dubois, 58, and his co-pilot standing by. Three hours out from Rio de Janeiro, Flight 447 was still on track.
The last crew conversation with on-ground controllers was routine. The co-pilot called out the plane's position using the internationally recognised phonic alphabet: 'Charlie Papa Hotel Quebec.'
But at 1.35am, all radio communications ceased. But for another 35 minutes, Flight 447's computer continued to send out automatic position reports by satellite to the Air France base at Charles de Gaulle airport.
A last reading showed a location at 2.10am, 70 miles from where the wreckage was discovered.
So what brought down the plane? Looking through meteorological data, the team discovered that there was a thunderstorm in the area at the time. But why would experienced pilots fly into a storm?
'The idea that a pilot would fly through a thunderstorm - no, absolutely not,' says aviation safety expert John Cox.
Several other flights that night took the same route as Flight 447, but the pilots made detours of up to 90 miles to avoid the storm system, which towered to an altitude of 50,000ft.
The investigating team believes that a smaller storm in front of the larger weather front confused the flight's radar system, so that the crew did not see the thunderstorm coming.
It meant they had no choice but to ride out the turbulence. The pilot would have slowed down the engines - the standard method for flying through such conditions.
At 2.10am - the plane's last known position - it appears that Flight 447 entered a rapidly developing storm system that its radar detected too late. A little more than four minutes later, everyone on board was dead.
So what happened in those critical intervening minutes? Just after 2.10am, the flight computer sent a torrent of automatic fault messages to Air France in Paris.
Called by one pilot 'the last will and testament of the aircraft', these messages show that Flight 447 suffered 24 critical faults in just four minutes and 16 seconds.
The first message showed that the autopilot had switched itself off, so the pilot had to take manual control. Then the systems controlling air speed and altitude failed.
In the cockpit, instrumental display screens would have gone blank, and flight-control computers would have died. One by one, the most critical safety features in the cockpit failed.
'It must have been a very busy and confusing situation on the flight deck,' says Cable.
It is a harrowing image, indeed. The cockpit would have filled with a multitude of audio and visual alarms, while the pilots desperately fought a losing battle to control the aircraft and keep it in the air as it was buffeted by a gigantic thunderstorm.
A final, ominous warning was sent by the plane to Paris: the Advisory Cabin Vertical Speed message, which means that the aircraft was descending at a high rate.
This last, terrifying message came just before Flight 447 and its passengers hit the water at hundreds of miles an hour. But what could have caused all the vital automatic systems to malfunction at once?
It appears that the three pitot tubes (speed sensors) failed simultaneously. It could be that they were unable to cope with the storm conditions facing Flight 447.
Accident investigators believe that super-cooled water in the clouds - well below freezing, but too pure to turn into ice - could have disabled the pitot probes.
Cable has discovered that since 2003, there have been 36 incidents involving frozen pitot tube on A330s or the similar A340s.
Indeed, in 2007, Airbus recommended a refit of all A330s with upgraded pitots. Flight 447 had not yet been refitted.
With no airspeed data, Flight 447's automatic systems would have collapsed one by one - which is exactly what happened.
It seems that in total darkness, and in the midst of a storm, the crew were forced to retake manual control of the plane.
John Cox explains how the pilots would have been bombarded with confusing information, saying: 'That crew faced an almost unheard of series of failures, one right behind the other.'
The most immediate danger was that the airplane would stall, which would lead to a sudden, uncontrollable descent (it had already slowed suddenly to cope with the turbulence).
Cox says: 'There is a good possibility that at some point in the last four minutes, it did stall.'
An unlucky series of events caused the accident, then, culminating in the automated systems failing and engines stalling.
Used to flying with high levels of automation, it seems the pilots did not have the skills to recover the situation.
Tragically, from the way the airline hit the water - nose up, with wings level - it appears that the crew may have come close to saving their passengers' lives.
It is likely they were recovering the situation but ran out of time, and suffered a second, and this time terminal, stall.
More than that, we will probably never know.
The airplane's black boxes, recording the last moments in the cockpit, stopped transmitting location signals after one month. Efforts to find them using imaging sonar continue.
So could such a tragedy happen again? Cable certainly believes that Flight 447 raises some vital issues for airlines.
'It has raised the question about whether the situation is actually being made worse by the increase in automation, whereby crews don't get a great deal of opportunity to manually fly the aircraft,' he says.
Airbus has also been criticised for not yet replacing all pitot probes in its fleet. In the face of new evidence, it maintains that even if they fail, pilots should be able to operate the plane.
A terrifying technical disaster, then, and one that led to a very human tragedy.
Alexander Bjoroy's parents held a memorial service for him last year, paying tribute to their son, saying: 'The world was his home. Alexander embraced other cultures and respected them greatly.
'He loved to travel and see and experience new places and people. We were very fortunate to share so many marvellous experiences together in his short life.'
The body of Swedish national Christine Schnabl was one of 51 recovered, but her five-year-old son Philipe was never found. She was not wearing a life jacket - it seems there was no time.
Her husband, Fernando, is preparing an album of pictures and cuttings to give to their daughter Celine when she is old enough to understand. One day, he hopes, he will be able to give her more answers.
For now, however, he simply tells her that her mother and brother have gone to a 'good place in the sky'.