Japan, a key U.S. ally, had sought the suspension of all non-emergency V-22 Osprey flights over its territory after one fell into the sea on Wednesday in western Japan.
Japan's Coast Guard has said one person was found and confirmed dead, and the search for the remaining seven aboard continues.
The Pentagon said on Thursday that it was still flying Ospreys for now, and that it was not aware of any official request for their grounding.
"We are concerned that despite our repeated requests, and in the absence of sufficient explanation (from the U.S. military), the Osprey continues to fly," he told a news conference.
The Japan Self-Defense Forces (SDF), which also operates Ospreys, has said it would suspend flights of the transport aircraft.
Persons:
Hirokazu Matsuno, Yoko Kamikawa, Rahm Emanuel, Robert Dujarric, Dujarric, Mariko Katsumura, John Geddie, Chang, Ran Kim, Gerry Doyle
Organizations:
Kyodo, REUTERS Acquire, Rights, Japan's Coast Guard, Pentagon, Ospreys, U.S ., Japan Self - Defense Forces, U.S, Pacifist Japan, U.S . Marine Corps, Tokyo's Temple University, Thomson
Locations:
Kagoshima prefecture, Japan, U.S, Tokyo