Safety regulators want to fine Boeing nearly $4 million, saying the company installed critical wing parts on 133 planes even though it knew the parts were faulty.
The Federal Aviation Administration announced the proposed civil penalty Friday.
The FAA action covers parts on Boeing 737s known as slat tracks, which sit at the front edge of a plane's wings and guide the movement of panels called slats. The slats help give planes more lift during takeoffs and landings.
The FAA said the tracks were made brittle during a process in which they received a coating of cadmium and titanium, and that suppliers notified Boeing of the problem. Boeing still submitted the planes for FAA flight approval even after deciding that the slat tracks "could not be used due to a failed strength test," according to an FAA statement.
Chicago-based Boeing did not immediately respond to a request for comment. The company has 30 days to respond to the FAA.
