The US Air Force announced late on 19 August the grounding of 82 of 969 Lockheed Martin F-16s still in service after finding structural cracks.

The grounding, which involves only the two-seat F-16D, could be lifted to allow aircraft to fly a limited number of flight hours with a temporary fix, the air force says.

Engineers are still analysing options for a permanent repair, the air force says.

The cracks, which were discovered in post-flight inspections, damage the canopy sill longerons in a space between the front and rear pilot seats, the air force says.

Longeron cracking caused a Boeing F-15C to disintegrate in flight in Novemeber 2007. That event triggered a grounding, fleet-wide inspection and lengthy repair.

The grounding underscores the air force’s aging inventory of fighters, as the service waits for the delayed entry and production ramp of the Lockheed F-35A. The 157 F-16Ds still in service are 24 years-old on average with 5,500 flight hours.

Lockheed is already performing a cycle of structural fatigue testing on an F-16 Block 30, which is unrelated to the inspections that discovered the canopy sill longeron cracks.

The fatigue tests are aimed at determining what structural modifications are necessary to extend the life of hundreds of F-16s by 10-15 years, depending on how long it takes for the F-35A to start replacing the fleet.