American Airlines crews had to inspect and test the exit slides on about 272 aircraft last week after a mechanic discovered a "potential problem" with the way the work had been done, the carrier said Monday.
The slides were found to be working on all of American's McDonnell Douglas MD-80 jets, but they had been packed and stowed on the planes using the wrong tool, said a spokesman for the airline.
"There were about 11 rafts that had potential issues, but none failed to inflate," said the spokesman, Tim Wagner.
The situation came to light when a mechanic notified American and the Federal Aviation Administration under a voluntary program of reporting potential safety issues without fear of retaliation from the airline.
Wagner said American notified the FAA that it would inspect and repack all the slides properly, and did the work from Wednesday night through Friday without affecting flight schedules.
The rear slides of the MD-80s must be unfolded, tested and repacked every 18 to 36 months, but the airline's crews were doing the work without using a tool designed by the manufacturer to realign parts of the slide, Wagner said.
The FAA did not immediately respond to requests for comment.