WASHINGTON and MANASSAS, Va. -  Defense Secretary Leon E. Panetta is satisfied the Air Force has identified the cause of hypoxia-like symptoms 12 F-22 pilots suffered, and restrictions he placed on use of the fifth-generation fighter will be lifted gradually.

Air Force Secretary Michael B. Donley, Air Force Chief of Staff Gen. Norton A. Schwartz and other Air Force leaders told Panetta on July 20 that they are confident the root cause of the symptoms is the supply of oxygen to pilots and not the quality of oxygen, Penta...