The Marine Corps made the announcement on Thursday.
The collision between a fighter jet and a refueling aircraft occurred about 100 kilometers off Kochi Prefecture early Thursday morning. The planes, carrying a total of 7 crewmembers, crashed into the ocean soon after.
Both planes operate out of the US Marine Corps Iwakuni Air Station in Japan’s western prefecture of Yamaguchi.
The aircraft were on a training mission at the time of the collision. But details remain unknown, including whether the accident took place while they were engaged in a mid-air refueling exercise.
Japan’s Defense Ministry is asking the US military for information.
Self-Defense Forces personnel are continuing their search for the missing crewmembers through the night.