This month marks three years since Malaysia Airlines Flight 370 disappeared. On March 8, while flying from Malaysia to China, the plane deviated from its planned route, slipping from the range of radar somewhere over the Andaman Sea. MH370 and its 239 passengers likely crashed somewhere in the Indian Ocean, but even after a massive search effort, the black box was never found—leaving the tragedy permanently shrouded in mystery.

The frightening truth is that planes are essentially unaccounted for quite frequently. When you’re flying on a plane and the screen in front of you shows your position over an ocean or the poles, it’s likely that you, the passenger, know more about your plane’s location than Air Traffic Control does. But that is starting to change.
How it works ?
Pilots use GPS to track their plane’s position, but that doesn’t mean an air traffic controller can always find them.

Radar measures a plane’s location by sending out pings of radio waves and measuring how long it takes for the signals to bounce off the aircraft—but that only works if the aircraft is within the radar tower’s line-of-sight, with no mountains or other solid objects in the way. Radar doesn’t work over long distances, so the oceans are a big blind spot.
Starting about 15 years ago, air traffic control started using ADS-B ground stations. ADS-B, which stands for Automatic Dependent Surveillance-Broadcast, tracks the airplane’s position via GPS, and automatically broadcasts that information to Air Traffic Control as well as other planes.

ADS-B receivers are “about the size of a mini refrigerator,” says Capezzuto, and because they’re much easier to install in hard-to-reach places, they’re already improving airplane tracking. In fact, the Federal Aviation Administration likes them so much, they’re requiring all planes that fly through controlled airspace to be equipped with these broadcasters by January 2020.
However, ground-based ADS-B receivers have many of the same line-of-sight problems as radar, and under clear conditions, they only have a range of about 250 nautical miles at 28,000 feet.
“You don’t really have an option for surveillance in the ocean,” says Capezzuto. “Right now, air traffic controllers project where the aircraft should be, based on the flight plan or the pilot report, rather than reality. Deviations in the flight plan happen all the time.”

Putting the ADS-B receivers onto satellites removes the line-of-site problems, giving a birds-eye-view of planes flying across the entire globe. After receiving location data from the aircraft, Aireon’s 66 satellites will beam the information down to ground stations. The entire transaction takes about two seconds.
Courtesy : Papular science