Why we may never find out what happened to MH370
British satellite firm knew flight likely to have taken one of two corridors day after it vanished
With all hope now lost of finding their loved ones alive, relatives of the 239 people on board flight MH370 were increasingly expressing anger and resentment towards those they believe are to blame for the failure to locate the missing aircraft.
By singling out the UK Air Accidents Investigation Branch (AAIB) and the British satellite firm Inmarsat as the sources of the information that confirmed the Boeing 777 went down in the Indian Ocean, Najib Razak, Malaysia's prime minister, may have directed part of that anger towards Britain.
The AAIB, working with Inmarsat, provided the only credible information on the Malaysia Airlines flight's whereabouts, but a series of delays meant 10 crucial days were lost before search teams began looking in the southern Indian Ocean, where it now seems certain the aircraft went down.
Inmarsat knew the day after MH370's disappearance that it was likely to have flown along one of two "corridors" that later became the focus of the investigation, but vital resources were expended on looking in the wrong places because of a seeming breakdown in communications. Exactly what went wrong, and who was to blame, remained unclear last night, but both the British and Malaysian authorities must brace themselves for a barrage of uncomfortable questions from loved ones of the dead.
The search for MH370 would have been hopeless had it not been fitted with a system called Classic Aero, a type of Aircraft Communications Addressing and Reporting System (ACARS) which transmits data on location, altitude, heading and speed. ACARS, as is now known, can be turned off manually, via a switch on the ceiling of the cockpit or behind the throttles between the pilot and co-pilot.
MH370's ACARS system was switched off at 1.21am on March 8, two minutes after the pilots' last verbal communication with the ground. It is this deliberate act that has convinced investigators the pilots were on some form of suicide mission.
But Classic Aero also has a second terminal that operates independently of ACARS and cannot be switched off while the aircraft still has power.
Once every hour the system sends out a "ping" to satellites operated by Inmarsat. The pings play no part in ACARS, and merely serve to synchronise timing information and keep the connection to the satellite network alive.
Inmarsat, which owns 11 telecommunications satellites, supports the Global Maritime Distress and Safety System free of charge, as a public service, to help locate stricken ships and aircraft.
The day after MH370 disappeared, Inmarsat began calculating the aircraft's movements based on the hourly pings, which carried on until 8.11am on March 8, meaning the 777 had flown for around six hours after it was last tracked by military radar off the west coast of Thailand.
The pings contain no information about location, heading or speed, meaning the only information Inmarsat had to go on was the wavelength of the pings when they reached its satellite orbiting 22,245 miles above the Earth.
Variations in the wavelengths proved that the aircraft was still moving until at least 8.11am. But they did not provide any clues about direction, meaning Inmarsat could only predict that it flew either north or south along two curved "corridors". By factoring in the aircraft's expected speed, Inmarsat worked out that the 777 was likely to have come down somewhere at the end of the two arcs.
Chris McLaughlin, the firm's spokesman, said: "What we discovered was a correlation with the southerly route and not with the northern route after the final turn that the aircraft made, so we could be as close to certain as anybody could be in that situation that it went south.
"Where we then went was to work out where the last ping was, knowing that the aircraft still had some fuel, but that it would have run out before the next automated ping. We don't know what speed the aircraft was flying at, but we assumed about 450 knots."
Inmarsat also refined its prediction by comparing the ping data with pings from previous, normal flights.
The company's calculations were based on inexact science, but they quickly predicted the Texas-sized area of the southern Indian Ocean where it is now accepted that the aircraft crashed.
Yet it took until March 18 before rescue teams announced they had narrowed down the search area to the location 2,000 miles west of Perth, where several sightings of debris have been made.
The terrible question now being pondered by relatives is whether anyone might have survived and could have been saved if the message had got through sooner. At the very least, opportunities to locate the Black Box data recorders may have been missed.
What caused the delay? Inmarsat initially shared its data with SITA, a Swiss aviation IT company, but for unknown reasons Inmarsat's calculations did not reach the Malaysian investigators until March 12.
Even then, it would be another three days before the Malaysians shared the information with the passengers' families and the public. And it took a further three days, until March 18, before Australia announced it had narrowed down the search area to a defined patch of the southern Indian Ocean.
Mr Razak is reported to have told his investigators that all raw data had to be corroborated with other agencies before it was released to the public. The Malaysian government has also suggested that it took a week to process all of the data it was receiving from multiple international sources and to eliminate red herrings.
According to 'The New York Times', US investigators tried telling the Malaysians they were looking in the wrong place a week after the aircraft disappeared, but their warnings were not heeded for several days.
France was said to have offered help on March 9 but was ignored for a week before the Malaysians finally agreed to meet experts who took part in the two-year search for the flight data recorders of the Air France jet that crashed into the sea north of Brazil in 2009.
Malaysian officials have also been accused of failing to share all the information from their own systems because they did not want to admit weaknesses in their radar and satellite operations.
And while international experts would normally be told within 24 hours about ACARS data, the Malaysians withheld it for several days. It was this information that suggested the Boeing 777 was deliberately turned to the west, away from its planned route to Beijing.
The most likely explanation for the delays appears to be distrust between Malaysia and the other countries involved in the search, according to experts.
Mr Razak announced yesterday that Inmarsat and the AAIB "have been able to shed more light on MH370's flight path". He said the new analysis showed that the aircraft's last position was "a remote location, far from any possible landing sites. It is therefore with deep sadness and regret that I must inform you that, according to this new data, flight MH370 ended in the southern Indian Ocean".
James Healey-Pratt, a lawyer representing some victims' families, said: "This investigation does not compare favourably to that of Air France 447, where the families felt they received information more accurately and quickly – without the trauma of having to endure an emotional roller coaster of wildly varying theories over the causes. Live streaming Black Box type data is the simple solution."