The US Marines have suspended flights of all Osprey military aircraft in Japan, after a crash off the coast of Okinawa island.
The incident on Tuesday night injured five crew members onboard.
It stoked immediate anger among locals, some of whom have previously complained about the US military bases and the Osprey aircraft’s safety record.
It combines helicopter and aeroplane capabilities and has been involved in accidents worldwide.
The most recent crash was in Hawaii in May last year, in which two US Marines died.
Tuesday’s incident took place near the controversial US Marine base Camp Shwab around 22:00 local time (13:00 GMT).
Pentagon spokesman Captain Jeff Davis described it as a “mishap” as the aircraft landed in shallow water, and said they would conduct an investigation.
The US maintains two Osprey squadrons in Japan. A squadron typically has between 12 and 24 aircraft.
Locals have long opposed the use of Ospreys, which are based in Futenma air station near densely populated neighbourhoods.
Okinawan governor Takeshi Onaga, known for critical view of US presence on the island, called the incident “really outrageous”.
“Although it occurred at sea, it’s really scary thinking it could have fallen on where we are living,” local resident Yuri Soma told Kyodo news agency.
Local anger against the US military has intensified in recent months after a civilian worker on a US base was arrested in May for the rape and murder of a local woman.
Okinawans have also opposed the government-approved relocation of Futenma air station in the middle of the island to Camp Schwab, as they want the bases to be removed entirely.