On February 23, 2008, a Northrop Grumman B-2 Spirit bomber, the Spirit of Kansas, crashed on takeoff from Andersen Air Force Base in Guam. The aircraft belonged to the 393rd Bomb Squadron, 509th Bomb Wing based at Whiteman Air Force Base, Missouri.
The subsequent investigation found that water from a heavy rainstorm had entered air data sensors, causing incorrect data to be processed by the flight computers.
Moisture in the aircraft's Port Transducer Units during air data calibration distorted the information in the bomber's air data system, causing the flight control computers to calculate an inaccurate airspeed and a negative angle of attack upon takeoff. According to the report, this caused an, "uncommanded 30 degree nose-high pitch-up on takeoff, causing the aircraft to stall and its subsequent crash."
Moisture in the PTUs, inaccurate airspeed, a negative AOA [angle of attack] calculation and low altitude/low airspeed are substantially contributing factors in this mishap. Another substantially contributing factor was the ineffective communication of critical information regarding a suggested technique of turning on pitot heat in order to remove moisture from the PTUs prior to performing an air data calibration.
(US Air Force)
Fortunately, both crew members ejected prior to the crash. The pilot was uninjured, but the co-pilot suffered a spinal compression fracture from the ejection. It remains the only crash of a B-2 bomber to date, and, at $1.4 billion a copy for the B-2, the most expensive write off in the history of the Air Force.
The Spirit of Kansas on static display in 1995