Colonel Cluff said top Pentagon officials thought last year that the Air Force could safely reduce the number of daily flights as military operations in Afghanistan wound down. But, he said, “the world situation changed,” with the rapid emergence of the Islamic State, and the demand for the drones shot up again.

Officials say that since August, Predator and Reaper drones have conducted 3,300 sorties and 875 missile and bomb strikes in Iraq against the Islamic State.

Image A Predator drone on a training flight from Creech Air Force Base, Nev., in 2009. Credit... Ethan Miller/Getty Images

What had seemed to be a benefit of the job, the novel way that the crews could fly Predator and Reaper drones via satellite links while living safely in the United States with their families, has created new types of stresses as they constantly shift back and forth between war and family activities and become, in effect, perpetually deployed.

“Having our folks make that mental shift every day, driving into the gate and thinking, ‘All right, I’ve got my war face on, and I’m going to the fight,’ and then driving out of the gate and stopping at Walmart to pick up a carton of milk or going to the soccer game on the way home — and the fact that you can’t talk about most of what you do at home — all those stressors together are what is putting pressure on the family, putting pressure on the airman,” Colonel Cluff said.

While most of the pilots and camera operators feel comfortable killing insurgents who are threatening American troops, interviews with about 100 pilots and sensor operators for an internal study that has not yet been released, he added, found that the fear of occasionally causing civilian casualties was another major cause of stress, even more than seeing the gory aftermath of the missile strikes in general.

A Defense Department study in 2013, the first of its kind, found that drone pilots had experienced mental health problems like depression, anxiety and post-traumatic stress disorder at the same rate as pilots of manned aircraft who were deployed to Iraq or Afghanistan.