The urgent need for more drones has meant bypassing usual procedures. Some of the 70 Predator crashes, for example, stemmed from decisions to deploy the planes before they had completed testing and to hold off replacing control stations to avoid interrupting the supply of intelligence.

“The context was to do just the absolute minimum needed to sustain the fight now, and accept the risks, while making fixes as you go along,” Colonel Mathewson said.

It is easier, of course, for the military to take more risks with unmanned planes.

Complaints about civilian casualties, particularly from strikes in Pakistan, have stirred some concerns among human rights advocates. Military officials say the ability of drones to observe targets for lengthy periods makes strikes more accurate. They also said they do not fire if they think civilians are nearby.

The Predators were still undergoing basic testing when they were rushed into use in Bosnia and Kosovo in the 1990s and then hastily armed with missiles after the September 2001 terrorist attacks.

But it was only after the military turned to new counterinsurgency techniques in early 2007, that demand for drones became almost insatiable. Since then, Air Force Lt. Gen. Gary North, the air-component commander for the combined forces in Iraq and Afghanistan, said the service has gone to “amazing lengths” to increase their use.

The Predators and Reapers are now flying 34 surveillance patrols each day in Iraq and Afghanistan, up from 12 in 2006. They are also transmitting 16,000 hours of video each month, some of it directly to troops on the ground.

The strains of these growing demands were evident on a recent visit to Davis-Monthan Air Force Base in Tucson, Ariz., one of four bases where Air National Guard units have been ordered to full-time duty to help alleviate crew shortages.