The Air Force has temporarily grounded 82 of its aging F-16 fighter jets after structural cracks were found near the cockpits.
The first cracks were discovered July 31 during post-flight inspections of a F-16D model, which is a two-seat variant primarily used for training. Subsequent inspections found that more than half of the F-16Ds were affected.
The grounding of the aircraft highlights an ongoing concern in the Air Force that its 2,028 fighter and attack jets are aging fast.
"As aircraft accumulate flight hours, cracks develop due to fatigue from sustained operations," Lt. Col. Steve Grotjohn, Air Force deputy chief of the weapon system division, said in a statement.
Individual units inspected the 157 F-16Ds to ensure structural integrity and pilot safety. The inspections, which wrapped up Monday, found that 82 had cracks; the other 75 aircraft returned to flight.
Officials said engineers from the Air Force and F-16-maker Lockheed Martin Corp. are developing temporary fixes to allow the aircraft with cracks to resume operations, while work continues on a permanent fix.
The cost has yet to be determined.
"Upon completion of this process, we will have a greater understanding of the scope of the stand-down as well as the total costs needed to mitigate any potential impact to the aircraft's safe and effective operation," said Capt. A.J. Schrag, an Air Force spokesman.
The F-16 is set to be replaced by the F-35 fighter jet, which is about halfway through its development plan and has been plagued by technical problems, delays and billions of dollars' worth of cost overruns.
Known as the Joint Strike Fighter, the nearly $400-billion program for more than 2,400 F-35s is centered around a plan to develop a fighter plane that could -- with a few manufacturing tweaks -- be used by the Air Force, Navy and Marine Corps.
The three F-35 variants are supposed to be stealthy, able to take off and land on runways and aircraft carriers, and hover like a helicopter. No other fighter aircraft has all those capabilities.
There are 969 F-16s of all variants in the Air Force. Only the D models had cracks on so-called canopy sill longerons, which are pieces of structure between the front and rear pilot seats.