Investigators determined that the pilot who was training to fly U2 spy planes either pulled back too fast or too quickly on his stick while learning to recover from a stall shortly after the plane left from Beale Air Force Base about 50 miles (80 kilometers) north of Sacramento, Air Force Major A.J. Schrag said.
"He probably got a little overenthusiastic," Schrag said.
That caused the plane to go into a secondary stall that forced the student pilot and his instructor, Lt. Col. Ira S. Eadie, to eject before the plane turned upside down. The $32 million plane crashed near Sutter, California.
Eadie suffered fatal injuries when his seat struck the plane's right wing, investigators found. The student pilot also suffered injuries, though he has since recovered and completed his training to fly U2 spy planes, Schrag said.
Schrag said privacy laws did not allow the Air Force to disclose the student pilot's name.
He was on the first of three "acceptance flights" that are part of the process of interviewing to be a U2 pilot, the Air Force said.
The U-2 "Dragon Lady" is a surveillance and reconnaissance plane capable of flying above 70,000 feet (21,336 meters). Developed during the Cold War to spy on the Soviet Union, the single-engine aircraft now carries high-resolution cameras and sensors to gather radio signals and other information useful to intelligence agencies and battlefield commanders.
The fleet is based at Beale, though U2 planes fly missions from other locations.
Before the crash, the Air Force said it had 33 U-2s. The U-2 is slated for retirement in 2019 as the military relies increasingly on unmanned aircraft for surveillance.
(Sudhin Thanawala - Associated Press)