How investigators found a jet engine under Greenland's ice sheet

Four hours into a September 2017 Air France flight 66 from Paris to Los Angeles, one of the aircraft's four engines spontaneously exploded. "IS THERE A PROBLEM," read the message from air traffic controllers to the pilots. The plane, with over 500 people onboard, was flying four thousand feet below its previous altitude and, indeed, there was a problem. The front portion of an engine had fallen off, plummeting more than seven miles to the frozen Greenland ice sheet below.