A small plane chartered by the U.S. Army Corps of Engineers crashed Thursday in western Alaska, killing all eight people on board, the U.S. military said. The plane was traveling to a remote aircraft-tracking radar site when it went down.

The crash happened near Cape Newenham Long Range Radar Site Airport, approximately 450 miles west of Anchorage. 

The twin-engine Cessna 441 was scheduled to land there after taking off from Ted Stevens Anchorage International Airport, the Federal Aviation Administration said Friday.

Clint Johnson, the National Transportation Safety Board’s Alaska region chief, said there were two pilots and six passengers on board. The U.S. Army Corps of Engineers said in a statement that two of its employees were among those killed.

“This is a devastating loss for our military family and the communities we serve,” U.S. Air Force Lt. Gen. Robert Davis, commander of Alaskan Command, the Alaskan North American Aerospace Defense Command Region and Eleventh Air Force, said in a statement.

The NTSB and FAA are investigating the crash. It happened in foggy weather, according to information from a service that’s part of the nonprofit Flight Safety Foundation.

The aircraft had attempted to land once before, resulting in a missed approach, and may have been coming back around for another attempt when they lost contact, Johnson said Friday during a virtual briefing. The plane crashed in rugged terrain in a very remote area, and it will take some time for the NTSB team to get there, he said.

Five NTSB investigators were traveling to the accident site, spokesman Peter Knudson said in a statement Friday morning. The wreckage will be documented and moved to a secure facility for further examination.

Investigators will look at weather conditions and what was communicated with the pilots, as well as other factors, Johnson said.

The airport is a private military site. The radar site is managed by the Pacific Air Forces Regional Support Center. It’s part of a network of remote radar sites that track aircraft operating in Alaska’s airspace and along its borders, the statement from Alaskan Command said.

The Corps said in a statement Friday that its two employees were “part of a project delivery team en route to a project site in support of the U.S. Air Force.” 

“We mourn the tragic loss of our selfless teammates. They were public servants and true professionals, dedicated to securing our nation,” Lt. Gen. William Graham, the Corps’ commanding general, said in the statement.

The statement from Alaskan Command did not provide details on the specific work the individuals were doing.

The Cessna aircraft was operated by Anchorage-based air charter company Security Aviation, according to the NTSB. 

Davis described those on board as “dedicated professionals carrying out a vital mission in a demanding environment. Our absolute priority right now is providing unwavering support to their families, friends and teammates during this devastating time. We are profoundly grateful for the swift and tireless response of our search and recovery professionals.”

“I join Alaskans in offering condolences as we learn of the plane crash in Cape Newenham,” Alaska Sen. Lisa Murkowski posted Thursday night. “I’ve traveled extensively with Security Aviation throughout Alaska, and have met many of their experienced pilots. I appreciate the U.S. Coast Guard, NTSB, Alaska State Troopers, and the Rescue Coordination Center for responding to the site. Alaska is praying for those on board, their loved ones, and the team at Security Aviation.”

In 1950, a continental defense radar station was built at Cape Newenham as part of the Distant Early Warning Line to warn of a Soviet attack during the Cold War, according to Coastview, a science education nonprofit that promotes understanding of the Alaska coast. Little remains of the former station today.