Accidents
In April 1992 the first YF-22 crashed while landing at Edwards Air Force Base, California. The test pilot Tom Morgenfeld escaped without injury. The cause of the crash was found to be a flight control software error that failed to prevent a pilot-induced oscillation.
The first crash of a production F-22 occurred during takeoff at Nellis Air Force Base on 20 December 2004, in which the pilot ejected safely prior to impact. The crash investigation revealed that a brief interruption in power during an engine shutdown prior to flight caused a malfunction in the flight-control system; consequently, the aircraft design was corrected to avoid the problem. All USAF F-22s were grounded for two weeks after the crash, but resumed operations after a review was completed.
On 10 April 2006, a pilot was stuck inside the cockpit of aircraft 03-041 for five hours when the canopy jammed.
On 25 March 2009 an F-22 crashed 35 miles northeast of Edwards Air Force Base during a test flight, resulting in the death of Lockheed test pilot David P. Cooley. The aircraft was from the 411th Flight Test Squadron. The Washington Post reported that the crash happened during a bombing test. An Air Force Materiel Command investigation found that Cooley momentarily lost consciousness during a high-G maneuver then ejected after finding himself too low to recover. Cooley was killed by blunt-force trauma during ejection because of the F-22's speed and the windblast. The investigation found no problems with the design or airworthiness of the F-22.
it's called upgrading and everyone does it, why do you think the F-16 has had so many block upgrades and so many sales? 
