из много раз упомянутой статьи в Washington Post

The Air Force has declined to discuss the cause, but a classified internal accident report completed the following month states that the plane flew into the ground after poorly executing a high-speed run with its weapons-bay doors open, according to three government officials familiar with its contents. The Lockheed test pilot died.

Several sources said the flight was part of a bid to make the F-22 relevant to current conflicts by giving it a capability to conduct precision bombing raids, not just aerial dogfights. The Air Force is still probing who should be held accountable for the accident.
Ну, отчета AIB недолго осталось ждать...