The Eagles were grounded after investigation of the 2 November crash of an F-15C determined the structural failure was caused by fatigue cracks in a fuselage longeron that had not been manufactured to blueprint specification.
After inspecting the entire fleet for cracks and non-specification longerons, the US Air Force on 8 January cleared 259 of its F-15A-D to return to flight. Cracks were found in nine aircraft and the remainder had longerons that did not meet specification and required further analysis.
The latest move leaves 162 F-15A-Ds still grounded and one pending clearance, says USAF Air Combat Command.
For more on the grounding, including video reconstructions of the in-flight breakup, read flightglobal's special report on the F-15 accident investigation.