TOKYO -- The pilot of the Japanese F-35A stealth fighter jet that crashed in April likely suffered "spatial disorientation," Japanese Defense Minister Takeshi Iwaya said on Monday.
Iwaya said the likelihood that the plane went down due to a technical problem was "extremely low." He said Japan's remaining 12 F-35As, which were grounded after the accident, will begin flying again soon, though he added that the timing "will be decided after taking measures to prevent a recurrence." The safeguards are to include pilot training and aircraft inspections.
The Ministry of Defense determined the likely cause of the accident by analyzing the jet's movements before the crash on the night of April 9.
The pilot, Maj. Akinori Hosomi, received instructions from ground control to put some distance between himself and a U.S. military aircraft that happened to be flying nearby. He made a left turn an descended from an altitude of approximately 9,600 meters down to 4,700 meters. The descent took 20 seconds, with the plane flying at a speed of over 900 kph.
Fifteen seconds later, the jet dropped to 300 meters above the Pacific Ocean, before vanishing.
Right after he began the left turn, Hosomi had calmly said, "Yes, stop training."
Investigators think that had there been a problem with the aircraft, it likely would have decelerated when descending. But the crashed jet was flying at nearly maximum thrust.
The F-35A is a cutting-edge aircraft developed mainly by the U.S. Some of the jets are assembled in Japan with American components, but a great deal of confidential information is withheld from the Japanese side. The Ministry of Defense has been looking into the crash with cooperation from the U.S.