British Satellite Company Inmarsat tracked the missing airliner by analysing the ‘pings’ picked up by one of its satellites from flight MH370.
The Telegraph reported that one of Inmarsat’s satellites had continued to pick up a series of automated hourly 'pings' from a terminal on the plane in spite of the main aircraft communications addressing and reporting system being switched off.
Inmarsat was able to establish that MH370 continued to fly for at least five hours after the aircraft left Malaysian airspace by analysing these pings.
According to the finding, the plane had flown along one of two 'corridors' – one arcing north and the other south. The plane was reportedly flying at a cruising height above 30,000 feet.
Senior vice president of external affairs at Inmarsat Chris McLaughlin said: "We looked at the Doppler Effect, which is the change in frequency due to the movement of a satellite in its orbit. What that then gave us was a predicted path for the northerly route and a predicted path the southerly route."
He said: "That’s never been done before; our engineers came up with it as a unique contribution."
The information was relayed to Malaysian officials by March 12 however; Malaysia's government did not publicly acknowledge it until March 15, reports The Wall Street Journal. .
Meanwhile, Inmarsat's engineers carried out further analysis of the pings and came up with a much more detailed Doppler Effect model for the northern and southern paths.
By comparing these models with the trajectory of other aircraft on similar routes, they were able to establish an "extraordinary matching" between Inmarsat's predicted path to the south and the readings from other planes on that route.
McLaughlin said by Monday they were able to definitively say that the plane had undoubtedly taken the southern route.
These pings from the satellite – along with assumptions about the plane’s speed – helped Australia and the US National Transportation Safety Board to narrow down the search area to just 3% of the southern corridor on March 18.
"We worked out where the last ping was, and we knew that the plane must have run out of fuel before the next automated ping, but we didn't know what speed the aircraft was flying at, we assumed about 450 knots,” he said.
"We can’t know when the fuel actually ran out, we can’t know whether the plane plunged or glided, and we can’t know whether the plane at the end of the time in the air was flying more slowly because it was on fumes," he added.
Inmarsat passed the relevant analysis to the UK Air Accidents Investigation Branch (AAIB) on Monday. The cause of the crash is yet to be discovered.