The US air force has begun grounding about a third of its active-duty combat aircraft because of automatic federal spending cuts, including squadrons of fighters, bombers and airborne warning and control craft.
The stand-down will affect units stationed in the U.S., Europe and the Pacific, though the Air Force didn't immediately provide a list of the units and bases that will be affected.
Some units that include F-16s, F-22s, A-10s and B-1s will be grounded after they return home from their deployments. Other units began the stand-down immediately.
"We must implement a tiered readiness concept where only the units preparing to deploy in support of major operations like Afghanistan are fully mission capable," Gen. Mike Hostage, commander of Air Combat Command said. "Units will stand down on a rotating basis so our limited resources can be focused on fulfilling critical missions."
The air force said the grounding was the result of cuts to the command's operations and maintenance account. The service says it must reduce its flying by about 45,000 fewer training hours by October 1 than previously scheduled.
"The current situation means we're accepting the risk that combat airpower may not be ready to respond immediately to new contingencies as they occur," Gen. Hostage said.
The airforce says it generally takes 60 to 90 days to conduct the training needed to return aircrews to mission-ready status. For affected units it will shift its focus to ground training.
That includes the use of flight simulators and academic training to maintain basic skills and aircraft knowledge.