The US Federal Aviation Administration (FAA) has proposed a civil penalty of $435,000 against United Airlines for allegedly flying an aircraft that was not in an airworthy condition.

According to FAA, the airline replaced a fuel pump pressure switch on one of its Boeing 787 planes on 9 June 2014. The replacement was carried out due to a problem that a flight crew had recognised two days before the repair.

“Maintaining the highest levels of safety depends on operators closely following all applicable rules and regulations."

The FAA alleged that following the replacement, United Airlines did not complete a required inspection of the repair, and reinstated the aircraft into service. The agency also alleged that the carrier flew the plane on 23 domestic and international passenger routes before performing the required inspection on 28 June 2014.

The FAA further noted that two of those flights occurred after the agency had notified United that it had not carried out the inspection.

The aircraft was allegedly not in an airworthy condition during all 23 of the flights.

FAA administrator Michael Huerta said: “Maintaining the highest levels of safety depends on operators closely following all applicable rules and regulations.

“Failing to do so can create unsafe conditions.”

FAA has also asked United to discuss the case with the agency.

Last week, FAA proposed a $63,000 civil penalty against Gladwin Paint Company in Arlington, Texas, US, for allegedly violating the Hazardous Materials Regulations.

According to the allegation, Gladwin offered a box containing flammable paint to FedEx for air shipment from Arlington to Abilene, Texas, last year.