The Air Force grounded more than 450 Boeing F-15 fighter jets on Wednesday after officials investigating a crash earlier this month found defects in the aircraft's fuselage.
It was the second time this month that F-15s were grounded. The entire fleet was grounded following a Nov. 2 Missouri Air National Guard training exercise in which a pilot safely ejected before the aircraft crashed. The Air Force subsequently returned the F-15s to flight status on Nov. 21.
The Air Force investigation, which is still under way, found there were "possible fleet-wide airworthiness problems" because of defects in metal rails that hold the F-15's fuselage together.
The Air Force said Wednesday that 452 of its oldest F-15s, or more than 60 percent of the fleet, will remain grounded until each one is inspected, and possibly repaired.
A Boeing representative could not be immediately reached for comment.
The Air Force seeks to replace aging F-15s, some more than 30 years old, with Lockheed Martin Corp.'s F-22 Raptor. The latest version of the F-15 is being used in operations in Iraq and Afghanistan. Non-combat but critical-mission flights were flown on Lockheed's F-16s while the F-15 fleet was grounded.
The F-15 was first manufactured by St. Louis-based McDonnell-Douglas, which was purchased by Chicago-based Boeing some 10 years ago. Boeing delivered its last military F-15 to the Air Force in late 2004, but still manufactures the aircraft for nonmilitary customers, the company said.