USA 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.
The U.S. Marine Corps said Thursday an FA-18 fighter and a KC-130 tanker aircraft were involved "a mishap" off the Japanese coast early Thursday.
There were five personnel on the C-130 and two on the F-18.
The US military has about 50,000 troops stationed in Japan and accidents are not uncommon. It was unclear if USA military officials were also assisting with the search.
3 astronauts safely aboard International Space Station
The crew was reporting that all was going well in the critical initial minutes after liftoff and were safely in orbit. Kononenko, McClain and Saint-Jacques showed no signs of worry as they boarded a bus to take them to the launch.
Salman Khan tops Forbes India celebrity list, again
Actor Akshay Kumar completed the top three, with Rs 185 crore in earnings in the period under consideration for the list. Brian Carvalho, Editor, Forbes India, said: "The Celebrity 100 is a definitive barometer of earnings of celebrities".