The global satellite network that convinced the FAA to ground Boeing’s 737 Max

A technician checks out a 737 Max in Indonesia.
A technician checks out a 737 Max in Indonesia.
Image: Reuters/Willy Kurniawan
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Even as nations around the world banned the Boeing 737 Max from their airspace this week, the US Federal Aviation Administration held firm. There were “no systemic performance issues” that its experts could identify linking the crash of a 737 Max in Indonesia last year and another in Ethiopia on March 10, and the flight data recorders from the latter accident had yet to be analyzed.

Then, the FAA suddenly decided to ground the widely used aircraft on March 13. Daniel Elwell, the acting FAA administrator, said he made the decision after viewing “refined” flight data provided by the company Aireon, which uses a network of satellites to provide the first real-time monitoring of aircraft around the world.

“At the request of the Federal Aviation Administration (FAA), The U.S. National Transportation Safety Board (NTSB), Transport Canada and several other aviation authorities, Aireon provided the data transmitted from Flight 302 to support the accident investigation,” Aireon said in a statement. “This unfortunate tragedy further highlights the need for a global, real-time air traffic surveillance system.”

Aireon’s analysis showed that Lion Air flight 610 and Ethio­pian Airlines flight 302 shared a similar flight profile before they crashed. That offers some confirmation that flawed pilot assistance software suspected of causing the first crash could also be the culprit in the most recent tragedy. Before the grounding, that software was still being used in cockpits carrying thousands of passengers.

The 737 Max, released in 2017, was designed to upgrade the range and efficiency of Boeing’s popular singe-aisle jet without starting from scratch. The new, larger engines and other design features left the aircraft with a tendency to stall in certain situations, a problem Boeing fixed with software that would force the nose of the airliner down.

But this software was not well explained to pilots, and crash investigators fear a lack of experience with the program, combined with malfunctioning sensors, could force the jetliners into dives their pilots could not escape. Boeing and the FAA are working on a patch to fix the software.

The data that Aireon used in its analysis comes from a system called ADS-B that air traffic regulators began to put in place a decade ago. Planes are required to use global positioning satellites to monitor their position, and broadcast out the details—location, altitude, speed—each second. Air traffic controllers collect the transmissions at ground stations, giving them a real-time picture their airspace.

Aireon, however, collects that data from a constellation of satellites that was completed earlier this year, though it is still certifying its system for integrated operations with air traffic controllers. Gathering ADS-B signals from space allows the company to spot planes over the ocean, where there are no ground stations, and maintain a record of air traffic in one database, not split by national territory.

The Lion Air crash took place within the coverage area of Indonesia’s ADS-B collection system, but according to captain Miguel Marin, chief of the International Civil Aviation Organization’s Operational Safety Section, the crash in Ethiopia “happened where ground-based ADS-B provides only limited coverage, and this is why the space-based data from the pre-operational Aireon network eventually had to be relied upon.”

Aireon said it provided the raw data, which takes time to analyze, to the FAA and the National Transportation Safety Board on March 11. The aviation regulator did not respond to questions about how it analyzed the data, but the two organizations are partnering to test out the monitoring service over the Caribbean this year.

Read more of Quartz’s coverage of the Boeing 737 Max crisis.