How Global Plane-Tracking System Will Work
The satellite company that tracked down the approximate location of the missing MH370 is now offering a free global airline tracking service.
So how will Inmarsat's plan work?
Every 15 minutes, a plane would send a bundle of information via Inmarsat satellite: its position, heading, altitude and speed.
Some 11,000 planes worldwide already use Inmarsat's satellite network - around 90% of the world's commercial fleet.
They use the links to maintain contact with air traffic, receive real-time weather information; or for passengers to use phones or internet on board.
The pings that Inmarsat analysed to locate MH370 were the periodic "hellos" exchanged between airplane and satellite to check whether a satellite channel was open, but contained no GPS or any other data.
Phone calls from a plane are famously expensive - and cost was cited as the biggest drawback by some airlines as the biggest objection to continuous flight data streaming.
Inmarsat says there will no installation cost for planes already using its services, and the company itself will foot the estimated $3m (£1.8m) annual bill for the service.
Inmarsat says it doesn't see the service as a sacrifice, but a way of driving its customers onto premium data services, beyond this basic tracking.
One of these is to reduce in-flight aircraft separation.
If aircraft are constantly reporting their position, altitude and speed, they can fly closer together.
This allows more efficient flight profiles and so fuel cost savings for airlines.
Inmarsat also plans to charge for a "black box in the cloud".
Whenever a plane went outside its expected parameters - for example, a sudden change of course - flight data recordings and cockpit voice recordings would automatically be streamed back to the ground via satellite.
So instead of spending months searching underwater for a small box, the information would arrive automatically at airlines' headquarters.
Others think that streaming flight data could bring other benefits, like more efficient diagnostics for planes, and quicker maintenance turnarounds, as I wrote a couple of months ago.
If airlines take up Inmarsat's offer, the black boxes of the MH370 may be the last we search for.