Seven Marines killed in copter training collision By Tim Gaynor PHOENIX (Reuters) - Two U.S. military helicopters collided during a training exercise over the desert along the Arizona-California border, killing all seven Marines aboard, the Marine Corps said on Thursday. The two aircraft, an AH-1W Cobra and a UH-1Y Huey, both attached to the 3rd Marine Aircraft Wing, were conducting nighttime training operations when the accident occurred about 8 p.m. local time on Wednesday. The five Marines aboard the Huey and the two aboard the smaller Cobra attack copter perished in the crash, said First Lieutenant Maureen Dooley, a spokeswoman for the 3rd Marine Wing, based at Marine Corps Air Station Miramar in Southern California. She said no other aircraft were flying with the two stricken copters, which collided over the Chocolate Mountain Aerial Gunnery Range in the southeastern California desert just west of the Arizona border. No one on the ground was involved in the accident, Dooley added. The two helicopters, although part of Miramar's 3rd Marine Wing, were both based at nearby Camp Pendleton, and six of the Marines killed were from Pendleton. The seventh was from Marine Corps Air Station Yuma, close to the crash site. Television images showed a scorched debris field in the desert where the helicopters fell. "Our airfield operations folks were contacted immediately and we began dispatching Marines to the scene to actually find out what's going on," Marine Gunnery Sergeant Dustin Dunk said. The Marines said the incident was under investigation and declined to say if initial information suggested what caused the accident. Dooley said weather and other environmental conditions did not appear to be factors in the crash, but she said she was unable to comment on whether the flight crews were using night-vision equipment at the time of the collision. U.S. Senator John McCain of Arizona, one of several politicians expressing their condolences, issued a statement lamenting the deaths and saying they were a reminder of the sacrifices of the U.S. military after a decade of war. Marine Corps Air Station Yuma lies in desert 2 miles west of Yuma, and the rugged terrain around the installation has made it an important training ground for Marines deploying to Afghanistan. More than a dozen military personnel have been killed in recent years from accidents involving the same types of helicopters that crashed on Wednesday night, most of them based in the San Diego area. Additional reporting by Steve Gorman, Phil Stewart and Dan Whitcomb; Editing by Peter Cooney