“There was good reason for killing the people that I did, and I go through it in my head over and over and over,” said Will, an Air Force officer who was a pilot at Creech and now trains others at Holloman. “But you never forget about it. It never just fades away, I don’t think — not for me.”

The complexities will only grow as the military struggles to keep up with a near insatiable demand for drones. The Air Force now has more than 1,300 drone pilots, about 300 less than it needs, stationed at 13 or more bases across the United States. They fly the unmanned aircraft mostly in Afghanistan. (The numbers do not include the classified program of the C.I.A., which conducts drone strikes in Pakistan, Somalia and Yemen.) Although the Afghan war is winding down, the military expects drones to help compensate for fewer troops on the ground.

By 2015, the Pentagon projects that the Air Force will need more than 2,000 drone pilots for combat air patrols operating 24 hours a day worldwide. The Air Force is already training more drone pilots — 350 last year — than fighter and bomber pilots combined. Until this year, drone pilots went through traditional flight training before learning how to operate Predators, Reapers and unarmed Global Hawks. Now the pilots are on a fast track and spend only 40 hours in a basic Cessna-type plane before starting their drone training.

Gen. Norton A. Schwartz, the Air Force chief of staff, said it was “conceivable” that drone pilots in the Air Force would outnumber those in cockpits in the foreseeable future, although he predicted that the Air Force would have traditional pilots for at least 30 more years.

Many drone pilots once flew in the air themselves but switched to drones out of a sense of the inevitable — or if they flew cargo planes, to feel closer to the war. “You definitely feel more connected to the guys, the battle,” said Dave, the Air Force major, who flew C-130 transport planes in Iraq and Afghanistan.

Now more and more Air National Guard bases are abandoning traditional aircraft and switching to drones to meet demand, among them Hancock Field, which retired its F-16s and switched to Reapers in 2010. Colonel Brenton, who by then had logged more than 4,000 hours flying F-16s in 15 years of active duty and a decade in Syracuse deploying to war zones with the Guard, said he learned to fly drones to stay connected to combat. True, drones cannot engage in air-to-air combat, but Colonel Brenton said that “the amount of time I’ve engaged the enemy in air-to-ground combat has been significant” in both Reapers and F-16s.

“I feel like I’m doing the same thing I’ve always done, I just don’t deploy to do it,” he said. Now he works full time commanding a force of about 220 Reaper pilots, sensor operators and intelligence analysts at the base.