Search operations were underway Wednesday for five US Marines whose helicopter failed to arrive in California as scheduled the previous day, the Marine Corps said.
The Marines were flying Tuesday on a CH-53E Super Stallion helicopter from Creech Air Force Base in Nevada to Marine Corps Air Station Miramar in southern California when "the aircraft was reported overdue," the service said in a statement.
"The 3rd Marine Aircraft Wing is coordinating search and rescue efforts with the San Diego County Sheriff's Department and the Civil Air Patrol," it added.
While the fate of the missing helicopter is still unknown, there have been a series of accidents involving US military aircraft over the past year, including the crash of a V-22 Osprey tilt-rotor aircraft off the coast of Japan in late November that left eight airmen dead.
Five American service members were killed when a helicopter crashed into the Mediterranean during a training exercise earlier the same month, while another Osprey crash in Australia left three Marines dead in August.
Three more military personnel were killed and another injured when two helicopters returning from a training mission in a remote area of Alaska collided in April.