American Airlines says its mechanics will fix floor mounts in 48 of its 757s to prevent seats from coming loose.
Three American planes had seats come loose while in flight recently.
The airline says engineers figured out "additional preventative steps" to upgrade the mechanism that locks the seats to the floor.
The carrier said 50 flights were canceled Thursday and 44 would likely be scrubbed Friday because of the work.
The Federal Aviation Administration says the agency agreed with the decision to repair the seat problem at each plane's next stop.