Boeing faces a possible fine of nearly $4 million after safety regulators say the company installed faulty parts on the wings of some Boeing 737 jets.
The Federal Aviation Administration says suppliers told Boeing about a problem with the components, which are known as slat tracks.
The parts sit at the front edge of a plane's wings and guide the movement of panels called slats, which help give planes more lift during takeoffs and landings.
The FAA says the slat tracks were weakened during a process in which they were coated with cadmium and titanium and became too brittle to meet safety standards.
Boeing has 30 days to respond to the FAA allegations.