Despite a series of crashes involving high-performance jet fighters, the armed services enjoyed their safest aviation year in history in fiscal 1988, the Pentagon said. The Navy, Marine Corps and Army each set individual records for aviation safety, and the Air Force came close to matching its all-time best, the Pentagon added. Combined, the four services flew their aircraft almost 7.3 million hours during the year ending Sept. 30, experiencing 137 Class A accidents. That amounts to a rate of 1.88 mishaps per 100,000 flying hours. A Class A accident is one in which there is either a fatality or damage exceeding $500,000.