DALLAS -- American Airlines aircraft seats that dislodged in flight, causing the temporary grounding of 48 Boeing 757s, already had been under closer scrutiny by the carrier for becoming loose sooner than others.

The airline initially blamed incorrectly installed saddle clamps before determining that a buildup of residue from spilled soda, coffee and juice had kept locking pins from remaining in place, David Campbell, American's vice president for safety, security and environmental, said in an interview Friday.

"We look every month because we have seen they were coming loose a little more than the average fleet we have," he said. "We have a very aggressive maintenance program."

Meanwhile, the airline said about midday Friday that all seat repairs on its Boeing 757 airplanes should be done by Saturday. American planned to cancel 44 flights Friday after it scrapped 50 flights Thursday because of the seat problem.

The seats were designed and made specifically for American by Zodiac Aerospace's Weber Aircraft Inc. unit in Gainesville, Texas. Robert Funk, vice president of sales and marketing for Weber, said in an email that he couldn't immediately respond.

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The 757 inspections initially began after seat rows in coach sections worked free on three flights from Sept. 26 through Oct. 1. Seat rows were tightened multiple times on at least one of two planes involved, and one set of seats came loose enough to shift backward. The seats never came completely loose from the floor, Campbell said.

The airline and Federal Aviation Administration are continuing an investigation into the incidents. American's mechanics are installing a redundant locking mechanism to address the issue.-- With AP