19th-century physics used to trace missing plane

Shortly after the plane went missing on March 8, Inmarsat used the ping data to plot two broad areas where the plane likely flew after it vanished from radar. One path took it north over central Asia, the other south to the Indian Ocean.

As days passed, more images and data became available, helping focus the search. But piecing that information together is time consuming and requires synchronizing the clocks of the various data systems, sometimes to a fraction of a second, said John Goglia, a former member of the US National Transportation Safety Board.

"Every time they get additional information from an additional site, they've got to go back and revisit what they've already done," Goglia said.

But the efforts are rewarded, he said, when all the sources of the data point to one spot at the same time.

The complexity of the work can take weeks, he added. "As difficult as this one was, I'm amazed that we've got some of what we've got so quickly," he said.

Inmarsat said for a relatively low cost its satellites could keep tabs on flights and provide data exchanged between the air and the ground to help organise routes to save time and fuel.

Its systems, which are widely used in shipping, have been embedded into surveillance and communications technologies that allow air traffic controllers to build up a picture of where aircraft are, and to better manage routes.

"If you have that (...) capability you get a preferred routing at the right altitude that makes your aircraft more fuel efficient, but if you don't have it you have to fly lower and get less priority in air-traffic control," said David Coiley, Inmarsat's vice-president for aeronautics.

The system is used in planes in the North Atlantic, Coiley told Reuters earlier this month, but it is not commonly used in all parts of the world.

Sinnatt said on Monday that such a facility would cost about $10 per flight. "It is something we have been pushing the industry to do because it significantly adds to safety," he said. Other satellite providers are also developing tracking systems.

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