The pilot reportedly ejected from the aircraft, although his present condition is unknown, Japanese authorities told local media.
The U.S. military says an Air Force F-15C fighter jet has crashed in waters south of Okinawa in southern Japan. Japan's public broadcaster NHK said he had a broken leg. The pilot is not in a life-threatening condition. The Kadena Air Base in Okinawa is the largest and most active US Air Force base outside the country's borders.
"Huge thank you to the Japan Air Self-Defense Force search and rescue team out of Naha Air Base this morning".
Onodera said he has asked the U.S. military to provide information about the accident, implement thorough safety management and take measures to prevent a recurrence.
"Accidents of USA military aircraft are occurring repeatedly", he said, according to the Kyodo news agency.
According to the report, Class A mishaps - those involving a fatality, US$2 million or more in damages, or a complete loss of aircraft - have increased almost 50% so far in 2018 over the previous year.
The F-15, belonging to the U.S. Kadena Air Base, crashed at around 6:40 a.m. about 80 kilometers south of Naha, the prefectural capital of Okinawa, the sources said.More news: Everything about Spider-Man for PS4 from E3
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In December 2017, two alleged incidents of parts falling from helicopters onto civilian territory occurred.
Kadena has temporarily paused F-15 training while the 18th Wing reviews "operational, maintenance and safety procedures with unit personal", the statement added.
"If that happens, we can not fulfill our responsibilities to our children and grandchildren", Onaga said.
The U.S. Air Force is also considering replacing the F-15s, worth around $36 million each, with F-16 fighting falcons by 2020.
Okinawa government officials asked the US military to suspend F-15 flights until their safety could be confirmed, Kyodo reported.
As Reuters additionally reported, the Japanese government is actively relocating the Futenma air base from its current location to the Henoko district of Nago city in the northern, and less populated, area of the island.