SAN DIEGO — The helicopter carrying five Marines that crashed during stormy weather in the mountains outside San Diego was a CH-53E Super Stallion designed to fly through bad weather, even at night.

The Super Stallion is the largest helicopter in the military, but every aircraft has its limits, and while every flight for Marines is considered a training opportunity, there is inherent risk, experts say. Now investigators will be looking at whether it was appropriate to send troops into a region being clobbered by a storm of historic proportions.

The military confirmed Thursday that all five Marines were killed when their helicopter went down during stormy weather, and efforts were underway to recover their remains.

Marine Corps leaders, Defense Secretary Lloyd Austin and President Joe Biden expressed their condolences.

“It is with a heavy heart and profound sadness that I share the loss of five outstanding Marines from 3d Marine Aircraft Wing and the ‘Flying Tigers,'” Maj. Gen. Michael J. Borgschulte, commander of the wing, said in a statement.

Authorities say the CH-53E Super Stallion vanished late Tuesday night while conducting a flight training on their way back to Marine Corps Air Station Miramar in San Diego from Creech Air Force Base, northwest of Las Vegas.

The last known contact with the Super Stallion was at about 11:30 p.m. Tuesday, when waves of downpours and snow were hitting the region, Mike Cornette of the California Department of Forestry and Fire Protection told CBS 8 news. That location was based on a “ping” reported to a Cal Fire dispatch center.

Marines fly the model in the “most challenging environments you can think of,” said Timothy Loranger, a former Marine Corps aircraft mechanic and now civilian pilot and lawyer who specializes in aviation crashes.

“But even knowing that, it’s important for those making the decisions to decide whether the risk is worth it,” he said. “Here was a training mission with the crew flying back home to Miramar, so you have to ask, why fly in this weather now? Was this poor judgement or some pilot error issue? These are very important questions that have to be asked.”

A mechanical issue in bad weather would also make flying even harder. And while the helicopter was designed for bad weather, ice accumulation on rotor blades could disrupt the ability to create lift for the craft and cause it to crash, Loranger said.