After 75 days of flying and bombing, the anxiety and uncertainties of combat had begun to give way to exhilaration among U.S. pilots here at Aviano Air Base, the busiest hub of the NATO air campaign.

The Serb-led Yugoslav government had accepted a Western peace plan to end the conflict over Kosovo. All that was required was for military leaders on each side to agree on when and how Yugoslav forces would retreat, and the air offensive would be over. Orders from NATO headquarters had limited the number and scope of air attacks.

Just Saturday, fresh from missions over Kosovo in which no bombs were dropped or missiles fired, a jubilant band of fighter pilots had burst into the squadron room here whooping: "We won the war! We won the war!"

Still, many pilots remained cautious -- a caution that proved justified early today as the talks on the promised Yugoslav troop withdrawal and refugee return broke down.

"I still have total and complete skepticism" about the peace deal, a 27-year-old pilot nicknamed "Dice" said yesterday, before it became plain that he and his squadron mates would likely be back in their cockpits for renewed heavy airstrikes against Yugoslavia. Dice, like other pilots here, agreed to be interviewed if his real name was not published; pilots cited security concerns that include their well-being if they are shot down.

NATO commanders were wary of Belgrade's peace pledge, as well. While the impasse on implementation dragged through a second day yesterday, U.S. B-52s bombed Yugoslav troops along the Kosovo-Albania border, where they have been battling separatist Kosovo Albanian rebels. Fighter pilots here also flew missions over Kosovo but said they were under orders not to attack unless responding to hostile action. None reported encountering any ground fire; most said Kosovo appeared quiet.

Whatever comes of current peace efforts, the past few days have given pilots here an unexpected respite to assess a war that -- to those who have fought it -- has been far more chaotic, complex and frustrating than the statistics and videos made public by NATO made it seem.

In interviews, the pilots described their current situation -- apparent victors in a conflict that is yet not over -- as among many unusual circumstances they have faced since the NATO air campaign began. One F-16 pilot, who flew his 29th mission of the war Saturday, confessed: "It'll be a great relief to get back to normal life. Everybody is just beat."

While NATO has not lost a single pilot in more than 10 weeks of airstrikes, those interviewed here cited other sources of anguish. They recounted their agony over bombing errors that killed innocent civilians and Kosovo rebels they were trying to assist; the frustration of witnessing atrocities by Belgrade government forces that they were helpless to stop; the exasperation over guided missiles that ignored their guidance; and the aerial traffic jams over Yugoslavia that sometimes seemed more dangerous than the antiaircraft fire from below.

Even as NATO commanders in Belgium and U.S. officials at the Pentagon detailed day after day of aerial pounding of Yugoslav ground forces in recent weeks, pilots based here said they were continually distressed by their inability to hit troops they knew had just left burning Kosovo villages that they could see from thousands of feet above.

"It tears your heart out," said a 33-year-old pilot called "Boomer," who has flown 41 missions in 75 days. "We've witnessed the atrocities. It's maddening to have to watch the destruction and be at a loss as to what to do about it. You want to be able to find [the Yugoslav troops], and they're so elusive.

"Up until the last two weeks, you could look anywhere in Kosovo on a clear day and see a village up in smoke," with sometimes as many as 60 houses burning. Boomer added, however, that in the last two days he has seen "no house fires and no wholesale strip burning of villages."

Despite some of the most sophisticated intelligence information and aerial imagery ever afforded combat pilots, Boomer said that the search for targets was often less than precise. He frequently served as a forward air controller, the aerial combat traffic cop who assigns as many as 30 inbound aircraft to their targets.

He said he would walk out of the "vault" -- the room in which pilots are briefed on targets by intelligence analysts -- with a stack of photographs identifying 25 to 30 potential mobile targets grouped in three categories according to their likelihood of being at a reported location: probable, possible or known.

"We didn't go out and find valid targets in every spot," he said. "Some days the Serbs had moved all the equipment." Over the past week, Boomer said, "I watched mortars impacting. I could see the impacts but not the mortar tubes firing, and the question was, `Who's firing?' " Uncertain whether he was overflying Kosovo rebels or Yugoslav forces, Boomer said he ordered no attack.

The errant NATO strikes on refugee convoys and a rebel outpost had a devastating effect on pilots, according to those interviewed here. "It crushes you any time something like that happens," said Boomer.

Aviano Air Base, usually home to about 3,500 U.S. Air Force personnel, more than doubled its population with an influx of additional U.S. and NATO forces supporting as many as 180 aircraft that have flown more than 37,000 hours of missions since late March.

For the pilots whose families live on the base or in the nearby Italian villages of narrow streets and red-tiled roofs, the daily transition from fighter pilot to husband and father was often unsettling.

"Your wife says you need to mow the lawn," said Dice, whose father also was an Air Force fighter pilot. "And you say, `Sorry, honey, I don't have time for that -- I've got to go drop bombs on Serbs.' "

For senior commanders of the air campaign, the test of the last 2 1/2 months shifted from coaching young fliers through heart-pounding fear to warning their now veteran pilots against complacency as hostile territory became all too familiar.

"There's a danger of pilots getting carried away," said Air Force Lt. Col. Steve Schrader, a squadron operations officer who flew his 38th mission this weekend. He said one of his pilots became so frustrated as frequent weather problems scuttled missions that he dove beneath the clouds to drop a bomb from a dangerously low altitude.

"He hit the target," said Schrader. "But when he got back here he had to deal with me."