Officials Tuesday suspended their massive search for 12 U.S. Marines who were aboard two helicopters that crashed off Hawaii last week.
The around-the-clock effort failed to locate any sign of the 12 service members despite five days of searching by several agencies.
Officials said at a late afternoon news conference that the search would be suspended at sundown and the Marine Corps would transition to "recovery and salvage" efforts. A memorial is tentatively planned for Friday at Marine Corps Base Hawaii in Kaneohe Bay.
"The decision to suspend the search without finding survivors is particularly difficult," said Capt. James Jenkins, chief of staff and acting commander of the Coast Guard 14th District in Honolulu.
The search began late Thursday when a civilian on a beach reported seeing the helicopters flying and then a fireball.
The Marines were alerted when the CH-53E helicopters carrying six crew members each failed to return to their base at Kaneohe Bay following a nighttime training mission. Hours later, a Coast Guard helicopter and C-130 airplane spotted debris about four kilometres off of Oahu.
The crash was near the north shore, but the search area spanned from the western coast of Oahu to the northeast corner of the island.
The transport helicopters were part of the 1st Marine Aircraft Wing at Marine Corps Base Hawaii. Known as Super Stallions, they are the U.S. military's largest helicopter, capable of carrying a light armoured vehicle, 15.5 tonnes of cargo or a team of combat-equipped Marines, according to a Marine Corps website.
The Coast Guard initially reported that the choppers had collided, but the Marines said later it wasn't yet known if there was a collision. The cause remains under investigation.
The Marine Corps will strive to "discover all of the facts" surrounding the crash, said Brig. Gen. Russell Sanborn, commanding general of the 1st Marine Aircraft Wing.
Round-the-clock search was employed
They will continue the recovery of any debris and "any other remains that may discovered," he said, "so that we can give closure to those families that are still out there that still want that final piece of the puzzle."
All four life rafts from the helicopters were found but they were empty. There was no indication anyone had been on any of the rafts, based on their condition and the lack of any personal effects, the Coast Guard said.
High surf complicated the mission for rescuers during the initial days of the search. A green laser near Haleiwa Beach Park struck a Coast Guard plane Saturday night, forcing crew members to alter search patterns.
Authorities searched for survivors around the clock. The Coast Guard assumes the best-case scenario when considering how long someone in the right equipment and right conditions could survive, Coast Guard Chief Petty Officer Sara Mooers said.
"We err on the side of caution because the last thing that anybody wants is to suspend the search when there's still a possibility of finding somebody," she said Monday.
Aircrews wear personal flotation devices with their flight suits and get additional training on top of survival swimming training, the Marines said.
People have been found days or even weeks after getting lost at sea, Mooers said.
The 12 missing men ranged in age from 21 to 41.