Nearly half of American Airlines' fleet of Boeing 757s -- 47 jets -- were taken out of service earlier this week to make sure that no more of its coach seats came loose in flight, as they now have three separate times. As of this morning, many of the planes are now back in service as the airline said the loose seats were a result of human or mechanical error and not sabotage.
The airline said a saddle clamp was improperly installed on the planes where the seats disengaged. The latest reported incident of loose seats occurred on a flight from Vail, Colo., to Dallas Sept. 26, the New York Post reported Tuesday.
Flight 443 from New York's John F. Kennedy Airport to Miami had to return to JFK Monday when the loose seats were discovered, the Federal Aviation Administration said in a statement.
The earlier reported incident took place Saturday night when seats came unbolted on American Airlines Flight 685 from Boston to Miami. The flight was diverted and made an emergency landing at JFK.
The FAA said in a statement Tuesday that it was looking into the first two incidents and that the airline's initial inspection of each aircraft had found other rows of seats that were not properly secured.
"Preliminary information indicates that both aircraft had recently undergone maintenance during which the seats had been removed and re-installed," the FAA said.
ABC News' Matt Hosford contributed to this report.