Navy officials said yesterday that their investigation into the fatal crash of an F-14 jet fighter in 1989 in Arizona revealed that the mishap occurred when the pilot and navigator removed their helmets and oxygen masks, donned their cloth garrison caps and saluted pilots in a nearby plane who were taking pictures of them.

Navy officials were responding to allegations made by a former top civilian Air Force safety official who said that the two men had removed their clothes and were attempting to moon colleagues in the other plane, and that authorities then attempted to cover up the cause of the crash in the subsequent report.

Navy spokesman Cmdr. Stephen Pietropaoli said the Navy's legal review of the case concluded that the men died of lack of oxygen after they removed their masks for what the report termed a "stunt," and turned off the plane's oxygen supply to cut down on the noise. They switched the oxygen back on too late and passed out.

Pietropaoli said it would be impossible, given the space constraints in the cockpit, for the pilots to have removed their flight suits. An autopsy report said the pilots were recovered fully clothed, the spokesman said.

The Arizona crash is one of 30 cases about which questions have been raised by Alan Diehl, who was the senior civilian Air Force safety official until last October when he was involuntarily removed. Diehl said yesterday that he was told of the alleged mooning by an Air Force investigator who had gone to the site immediately after the crash, and that a Navy investigator had talked about the mooning.

Diehl said the Air Force investigator had given him permission to turn his name over to a blue ribbon panel convened this week to investigate the Air Force's handling of air accidents.

Diehl's allegations have sparked investigations by the inspector general and the General Accounting Office.

This week Air Force Chief of Staff Gen. Ronald Fogelman convened a blue ribbon panel "because we've had 18 {major} mishaps since January 1, and 10 in the last two months and in light of recent published allegations concerning the quality and objectivity of the Air Force safety program," he said in a statement.