LOS ANGELES (AP) — The eight men killed in this week’s fiery crash of a B-52 during a test flight at California’s Edwards Air Force Base included four active duty airmen, a reservist and three civilians who were on a team devoted to keeping the bomber flying for decades to come, military officials said Wednesday.

The airfield where the Boeing B-52 Stratofortress crashed shortly after takeoff on Monday remained closed but other base operations have resumed, according to a base spokesperson. No cause has been determined. Officials said it could take six months to complete the investigation.

The victims were identified as: Col. Gregory Watson, 53; Retired Lt. Col. Miles Middleton, 50; Lt. Col. Gabriel Estrella, 40; Maj. Alexander Davis, 34; Maj. Robert Dee, 40; Maj. Brad Hovey, 35; Jeromy Smith, 32; and Christopher Rischar, 41.

“They were dedicated professionals, beloved family members and irreplaceable teammates,” Col. Thomas Tauer, commander of the 412th Test Wing at Edwards, said in a statement.

Watson, a weapons systems officer, and Middleton, a pilot, were Boeing employees and the company said their loss “is deeply felt across our teams, and our hearts remain with their families, loved ones and those who worked with them.”