Two Marine helicopters that crashed at night, killing 10 servicemen, apparently collided less than 200 feet above the Arizona desert, officials said.

The Boeing CH-46 and Bell UH-1N helicopters were on a training mission when the crash occurred Tuesday. A memorial service for the nine Marines and one Air Force officer killed was set for Friday afternoon at the chapel of the Marine Corps Air Station here."We feel confident enough to say a midair collision was more than likely," said Gunnery Sgt. Hal Wheeler, a spokesman at the Air Station.