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 US Marine Corps said an F/A-18 fighter jet and a KC-130 tanker aircraft were involved in the accident, which happened off the southwestern coast of Japan during "regularly scheduled training" on Thursday. Search and rescue efforts were ongoing, United States and Japanese officials said.
It was not clear how many crew members were on each of the planes.
Hands On With Samsung and Verizon's First 5G Phone
According to the leaks, the Qualcomm Snapdragon 855 will be the first mobile processor to support multi-gigabit 5G connections. Together, Samsung and Verizon have made huge gains in bringing 5G commercial services to consumers in several cities.
There is no official word on where the incident took place.
United States officials, speaking on condition of anonymity to Reuters, said one of the aircraft was an F/A 18 fighter jet while the other was a KC-130 refuelling aircraft, with a combined total of seven personnel aboard.
It says the Japanese search and rescue aircraft immediately responded to aid in recovery efforts and says the circumstances of the incident are under investigation.
Tyson Fury calls out Anthony Joshua after split draw with Deontay Wilder
I'm staying in downtown LA but if you go five minutes down the road there's like - I don't know - thousands of homeless people. Fury struggled to generate consistent offense until a strong sixth round, likely costing himself early rounds.
Early reports that surfaced on Twitter report that an F/A-18 (unspecified variant) and a C-130 crashed into the sea with a total of seven crewmembers on board.
Both aircraft are reported to have crashed into the water.
The US military has about 50,000 troops stationed in Japan.
Cosla gives backing to People’s Vote on Brexit
Mrs May's comments came as International Trade Secretary Liam Fox insisted that a no-deal Brexit would not be a disaster. They say May's Brexit deal was negotiated without taking into account their views, something the government denies.