Inspectors have found structural flaws in about 40 percent of the U.S. Air Force's F-15A-D fighter aircraft, the service said Wednesday, raising questions about their long-term viability. The Air Force grounded all 665 of its F-15 fighters in November after one broke apart in the air. After more than two months of inspections, the Air Force said 295 F-15 fighters of the “A” through “D” models have been cleared to fly again. But inspectors found nine aircraft with cracks in the thin strips of metal to which the aircraft's skin is attached, called longerons. The defect was the cause of the November F-15 crash. About 90 percent of the F-15 fleet has been inspected, so the Air Force faces a decision on whether to repair or retire the more than 100 aircraft with the structural flaws. Some older F-15s already had been scheduled for retirement, starting in 2009, and the cost of replacing a defective longeron is about $200,000, Air Force officials said. Long the top U.S. fighter jet, the F-15s now have an average age of about 25 years. The F-15E, the most advanced model in the line, is used for combat in Iraq and Afghanistan, but the older A through D models are mainly used to defend U.S. airspace. F-15s are gradually being replaced by the F-22, a faster, stealthy airplane, but the Air Force says it needs more than the 183 F-22s that it has been authorized to purchase. Air Force leaders have sought authority to buy 381 F-22s.
