WASHINGTON (AP) – Boeing Co., working with federal safety officials, is investigating tiny scratches on some older model planes to see if they are evidence of a potentially dangerous problem with the jets’ outer shells.

The scratches, or scribe marks, occur when a plane is prepared for repainting, said Boeing spokesman Jim Proulx. Workers scrape off a sealant used on the joints that hold together sections of the aircraft’s aluminum skin, he said.

The scribe marks can lead to deeper cracks that can spread, potentially leading to an uncontrolled decompression that can strip off pieces of the skin, according to an FAA safety bulletin issued late last year.

Proulx said Boeing will issue a bulletin to airlines later this year telling them to inspect planes once they’ve taken off and landed about 4,500 times after being repainted. An inspection involves taking the paint off along the joints to make sure there isn’t any scribing, he said.

The Federal Aviation Administration is considering following up with an order to inspect repainted planes and to repair them if cracks are found, said agency spokeswoman Diane Spitaliere.

The problem came to light during routine maintenance last October, Spitaliere said. Inspections began on about 80 aging jetliners that had been painted in the past few years, she said. Only two have been found to have cracks.

About 60 Boeing planes have been found to have scribe marks, Proulx said. The vast majority are 737s, the world’s most popular plane with about 2,800 in service. The 737s tend to be older – and to have been repainted more often – than other aircraft.

Also found to have the scribe marks were a few 747s, one 757 and one 767, Proulx said. The carriers themselves conducted most of the inspections.

Planes found with scribe marks were permitted back in service, but they must be inspected every 250 flight hours to make sure the scratches don’t become cracks, Spitaliere said. For the hardworking 737, that works out to about once a month.

FAA spokesman Les Dorr said the agency, the airlines and Boeing formed working groups in February that meet every six weeks and hold a weekly conference call to discuss the issue.

“Everybody’s been put on notice to look for these things,” Dorr said.

The FAA has also ordered airlines to repaint airlines at maintenance facilities where they will receive close scrutiny.

“This is a good example of how the safety system works,” Spitaliere said.

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On the Net:

Federal Aviation Administration: http://www.faa.gov

AP-ES-10-27-04 1656EDT