The Federal Aviation Administration (FAA) proposes a $5.4 million civil penalty against Boeing for installing nonconforming parts on about 178 737 Max aircraft.
The allegations against Boeing include installing nonconforming slat tracks, flaps on the on plane's wings that assist with lift on takeoff.
"Slat tracks are located on the leading edge of a Boeing 737’s wings and are used to guide the movement of panels known as slats. These panels provide additional lift during takeoff and landing," the FAA explains.
The FAA says "Boeing subsequently presented as ready for airworthiness certification."
The FAA accuses Boeing of failing to adequately oversee its suppliers to make sure they complied with the company's quality assurance system.
The agency says the failure resulted in slat tracks that were weakened and that Boeing knowingly submitted aircraft for final FAA-worthiness certification "after determining that the parts could not be used due to a failed strength test."
The FAA says Boeing has 30 days after receiving the agency's letter to respond.