US President Donald Trump inspected Japan's largest warship, the Kaga, during a state visit to the country.
The vessel is a helicopter carrier designed to carry submarine-hunting helicopters to distant waters, but will soon be upgraded to handle short take-off and vertical landing jets.
The refit of the Kaga, and its sister ship, the Izumo, is expected to bolster US forces operating from Japan by providing a refuelling platform.