The F-35 test fleet has been cleared for flight, but the Air Force's production aircraft at Eglin Air Force Base, Fla., are still grounded, the Pentagon said Thursday. An Air Force safety board is continuing its investigation of the failure of the AF-4's Integrated Power Package on Aug. 2, which led to the grounding of the fleet of 20 aircraft. Ground operations of the test fleet resumed Aug. 10. (Source: Air Force Times, 08/18/11)