WASHINGTON (CNN) -- A week after lifting a flight ban on more than 400 F-15 fighters, the U.S. Air Force once again grounded most of the fleet because of potential problems that could lead to the planes falling apart in mid-air.
The Air Force regrounds all F-15 A through D models after tests find problems with key strips of metal.
All 442 F-15 A through D models in the Air Force inventory were regrounded this week after inspectors looking at the November 2 crash of an F-15C found "possible fleet-wide airworthiness problems," a statement from the Air Force said.
Tests on the plane appear to have found problems with strips of metal -- called longerons -- which hold the fuselage together, Air Force officials said.
The planes must all go through more inspections and repairs if needed.
The fighter jets were inspected and cleared earlier this month after the entire fleet of 700 F-15s was grounded following the incident earlier this month, when a Missouri Air National Guard F-15C disintegrated in midair over Missouri. The pilot ejected safely.
Newer F-15E models were first cleared after being inspected, and last week the older F-15 A through D models were cleared after being inspected.
The E model -- in production since 1989 -- is not a part of the latest grounding.
"Although the longeron area was covered in general by previous inspections as a result of the November 2 mishap, technical experts with the Warner Robins Air Logistics Center, assisting in the Accident Investigation Board, have recommended a specific inspection of the suspect area based on the recent findings," the statement said.
"Manufacturer simulations have indicated a catastrophic failure could result in this particular area," according to the statement.
The grounding of the Boeing-made F-15 will not affect air operations in Iraq or Afghanistan because the F-15E flies there, according to Pentagon officials.
The grounding does slightly affect the homeland security operation called "Operation Noble Eagle," as the Air Force has had to fill gaps with F-16s.
Those missions are flying as usual and the grounding has had no impact on security, said officials with the North American Aerospace Defense Command.
Some of the F-15 A through D models have been flying for 23 years, according to Air Force records.
The F-15E Strike Eagle is an air-to-ground and air-to-air fighter, making it more versatile than other F-15 models, which are used for only air-to-air missions. E-mail to a friend