Yokosuka - Commanding officer Bryce Benson of the US warship USS Fitzgerald and several other crew have been airlifted to hospital after their navy destroyer collided with a much larger container ship, crushing the side of the militarty vessel.The US and Japan were on Saturday conducting a major search to find seven missing American sailors.Planes, boats and helicopters scoured the seas off Japan's Pacific coast in a bid to find the crew who disappeared in the predawn accident.The collision between the 154m guided missile destroyer and 222m Philippine-flagged container ship ACX Crystal happened off the coast of the Izu peninsula, southwest of Tokyo.Lying on stretcherThe US warship was pulled by a tugboat as it limped back to base in Yokosuka, where the navy said divers were trying to reach parts of the vessel smashed in the accident.It was not clear where the missing sailors - still unaccounted for nearly 20 hours later - were when the huge vessels collided the destroyer."This has been a difficult day," said Vice Admiral Joseph Aucoin, commander of the US 7th Fleet.The ACX Crystal had large scrapes on its bow, but none of its 20 crew was injured, Japan's coastguard said.Aerial television footage showed one person lying on a stretcher and a rescuer being pulled up to a helicopter that was hovering above the Fitzgerald.The accident happened 104km southwest of Yokosuka, in a busy shipping channel that is a gateway to major container ports in Tokyo and nearby Yokohama."The volume of ships is heavy in this area and there have been accidents before," coastguard official Yutaka Saito told Japan's public broadcaster NHK.Massive container vesselNHK said the massive container vessel made a sharp turn around the time of the collision with the smaller US warship, but its captain suggested otherwise.Japan's coastguard, which is probing the incident, said it had sent a half dozen vessels, several aircraft and a team of specially-trained rescue personnel to the scene. They were later joined by Japan's Self-Defence Forces.The US destroyer was commissioned in 1995 and deployed in the Iraq war in 2003.The navy said the crash caused "significant damage" and flooding in two berthing spaces; a machinery space and the ship's radio room."It remains uncertain as to how long it will take to gain access to the spaces in order to methodically continue the search for the missing," the navy said after the ship docked on Saturday evening.The ACX Crystal - which sailed to a Tokyo port on Saturday - is a commercial container ship with a Filipino crew, according to its Japanese owner, NYK Line.