After being grounded for months following a crash last November that killed eight service members in Japan, the V-22 Osprey - a complicated aircraft that flies fast like a plane but converts to land like a helicopter - is back in the air.
But there are still questions as to whether it should be.
Since the military started flying the aircraft three decades ago, 64 personnel have been killed and 93 injured in crashes. Japan's military briefly grounded its fleet again late last month after an Osprey tilted violently during takeoff and struck the ground.
To assess its safety, The Associated Press reviewed thousands of pages of accident reports and flight data obtained through the Freedom of Information Act, interviewed more than 50 current and former program officials, crew members and experts, and flew both simulator and real training flights.
The AP found that safety issues have increased in the past five years and that the design of the aircraft itself is directly contributing to many of the accidents.
