The US Department of Transportation’s Federal Aviation Administration (FAA) is proposing a US$435,000 civil penalty against United for operating a B787 aircraft that was not in an airworthy condition, it says.

The governing body for US aviation alleges that on June 9, 2014, United mechanics replaced a fuel pump pressure switch on the Dreamliner in response to a problem that a flight crew had documented two days previously.

But the airline then failed to perform a required inspection of the work before returning the aircraft to service, the agency alleges.

“United operated the aircraft on 23 domestic and international passenger flights before performing the required inspection on June 28, 2014,” an FAA statement reveals.

Two of those flights allegedly occurred after the FAA had notified United that it had not performed the inspection.

The FAA claims the aircraft was not airworthy during all 23 of those flights.

“Maintaining the highest levels of safety depends on operators closely following all applicable rules and regulations,” stresses FAA Administrator Michael Huerta.

“Failing to do so can create unsafe conditions.”

United has requested a meeting with the FAA to discuss the case.

United’s public image has suffered a tough year.

The airline was pelted with bad press coverage after a passenger was violently dragged off one of its flights in April after refusing to give up his seat. Video footage of the embarrassing encounter quickly went viral.

The airline has since settled a suit brought by passenger Dr David Dao, for an undisclosed amount.

Smaller incidents, such as the three-foot-long rabbit found dead after it flew with United Cargo, have also damaged the company’s public image.