HAGATNA, Guam (AP) — The Air Force investigated the first crash of a costly B-2 stealth bomber after one plunged to the ground Saturday shortly after beginning the last flight of a four-month deployment.

Both pilots ejected safely, though one was being transferred to Tripler Army Medical Center in Honolulu to be treated for spinal compression, said Tech. Sgt. Tom Czerwinski of Pacific Air Force's public affairs office in Hawaii.

Four of the bombers were taking off at the end of deployment to Andersen Air Force Base, officials said. At least one had taken off safely but was brought back after the crash.

The distinctive, bat-like B-2 is described as a "multi-role bomber" that blends stealth technology with a highly efficient aerodynamic design. It is able to deliver large payloads at great range and has been used in combat over Kosovo, Afghanistan and Iraq.

Each costs about $1.2 billion to build. The three that did not crash were being kept on Guam, said Maj. Eric Hilliard at Hickham Air Force Base in Hawaii.