The Air Self-Defense Force concluded Friday that the April crash of an F-35A stealth fighter in the Pacific Ocean was caused by "spatial disorientation" on the part of the pilot and not by any mechanical problem.

The conclusion is in line with an interim investigative report in June that pointed to human error. The report's findings were based on the ASDF's probe as well as expert analyses of radar data and communication records involving other F-35As that were training with the plane in question at the time of the crash on April 9.

In compiling the final report, investigators found that the pilot did not have enough time to stabilize the aircraft after a warning alarm went off, the ASDF said. The interim report concluded the pilot crashed without realizing his plane was barreling toward the sea.