In that crash, nine crew members died in test training at the Mather Air Force Base near Sacramento, The Associated Press reported at the time. The B-52 Stratofortress in Monday’s crash was on a routine test mission that took off at 11:20 a.m. local time at the remote air base, officials said. It is now considered a recovery operation.

“It was tragic and unsurvivable,” Colonel James Hayes said at a news conference. Emergency crews responded immediately to the crash involving the bomber, which left a towering black plume in its wake, the base said. Teams are working to notify families about the deaths over the next several hours, Chief Master Sgt. Joshua T. Skarloken said. The crew was a mix of military officials, government civilians and government contractors, Skarloken said.