The FBI is investigating the punctures that were discovered by on the underside of the planes by US Airways mechanics during their routine "walk around" checks, the Charlotte, N.C. Observer reported.
No passengers were aboard the planes, which were temporarily grounded for repairs, the report said.
The airline said the planes had punctures about the same size as holes a screwdriver might make. Airline spokesman David Castelveter characterized the holes as minor exterior damage.
The company is trying to reorganize in bankruptcy court.
The FBI is "very aggressively investigating anyone who had access to the planes," Kevin Kendrick, FBI special agent in charge for North Carolina, told the newspaper.
Earlier this week, the FBI said it was investigating mysterious holes found on a plane that had flown to Orlando, Fla., after a stop over in Charlotte.
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