It's addressing the same problem that caused the airline to ground 48 planes last week - the seat rows aren't locking properly into tracks on the floor.
Crews will add a "secondary locking device" to seats in most of American's Boeing 767s, spokeswoman Andrea Huguely said Friday. Those are wide-body planes used on international flights.
Seats came loose on three U.S. flights involving two different Boeing 757s earlier this month. There have been no similar mid-flight incidents with the Boeing 767s, but the airline is reinforcing the locking systems as a precaution, Huguely said.
In a memo, American assured employees that no other planes in the fleet have the same locking device. The seats involved are made by Weber Aircraft LLC, which did not immediately return calls for comment.
Work on the 767s started late Thursday and will be done by Oct. 21, Huguely said. The work will be done overnight and the airline won't have to cancel any flights this time. It canceled at least 94 flights because of seat problems with the 757s.
The Federal Aviation Administration said it approved of American's approach with the 767s. The FAA will let American keep flying planes that have not yet undergone the modifications.
Loose seats on the 757s raised safety concerns and turned into a public-relations nightmare for American, the nation's third-largest airline, which has been flying under bankruptcy protection since last November.
The FAA is still investigating the incidents on the 757s. Network TV news anchors and late-night talk-show hosts made fun of the airline. Jay Leno joked on NBC's "The Tonight Show" that the airline had a new slogan: "Contents of plane may shift during the flight."
American first gave one explanation for the problem aboard its 757s, then gave another two days later, saying pins that hold the seats to the floor had become gummed up over time from dirt and by passengers spilling sodas and coffee. The seats had been removed and reinstalled, which American's vice president of safety, David Campbell, said could have made the loose-seat problem pop up sooner.
The reinforcing work will be done on 49 of American's 58 Boeing 767-300 aircraft. The other nine, along with 15 Boeing 767-200s, have different seats and were not part of Friday's announcement, according to the airline.
American is owned by AMR Corp., based in Fort Worth, Texas.
(Copyright 2012 by The Associated Press. All Rights Reserved.)