Last month, a U.S. Navy F/A-18 Hornet from the aircraft carrier USS Ronald Reagan crashed into the sea southwest of Japan's southern island of Okinawa, though its two pilots were rescued safely.
"Search and rescue operations continue for U.S. Marine aircraft that were involved in a mishap off of the coast of Japan around 2:00 a.m. December 6.", a Marine Corps news release said.
A spokesman for Japan's Self-Defense Forces said that one of the airmen had been rescued but the immediate fate of the remaining crew members was unclear.
The aircraft had launched from Marine Corps Air Station Iwakuni and were conducting regularly scheduled training when there was a "mishap", the Marine Corps said.
The planes involved are a KC-130 and an F/A-18 based at Iwakuni near Hiroshima and were carrying seven personnel, Marines officials said.
The military did not release the circumstances of the crash, saying the accident was still under investigation.
The Marine Corps said Japanese search-and-rescue aircraft immediately responded to aid in recovery efforts. Officials said the information was provided by the USA side.
There were five personnel on the C-130 and two on the F-18.
More than 50,000 US troops are based in Japan under the bilateral security pact.