Some 34 A-10 Thunderbolt II jets flown from Davis-Monthan Air Force Base have been grounded indefinitely.
The cracks had the potential to cause the wings to fall off, a military aviation expert said.
As a follow up, the Air Force Friday ordered immediate grounding of about one-third of the approximately 400 jets in use across the globe.
Davis-Monthan has responsibility for 82 of the A-10s. Of that number, 34 were grounded for inspection and repair due to the Air Force order.
Tucson, Ariz., is home to the worldís largest fleet of the A-10s, with Davis-Monthan one of the nationís top training sites for the aircraftís pilots.
The jets were first introduced 33 years ago, and have surpassed their normal life span. They have been refurbished to keep them in service. Production on new aircraft ceased more than 20 years ago.
The grounded A-10s all have thin-skin wings installed during original manufacture, Air Force officials said.
The discovery of wing cracks is a ìserious issue,î said Davis-Monthan wing commander Col. Paul Johnson, adding that must be addressed to protect pilots and the public.
The commander added that the Air Force is fortunate to have keen-eyed maintenance personnel who noticed the problem before it caused any accidents.
The Tucson base will use flight simulators as a way to minimize the impact on trainees, but ìultimately we may be forced to delay the graduation of some of our pilots,î Johnson said.
ìThe Air Force is acting prudentlyî by grounding the aircraft, said military aviation expert Peter B. Field. He is a retired Marine Corps pilot who has worked for major aircraft manufacturers.
A jetís wings flex with every flight, he said. Over time, the wings of older aircraft, such as the A-10, built before sturdier metal composites came into use, will begin to weaken along the flex lines.