A United Airlines Boeing 787 taxis as a United Airlines Boeing 767 lands at San Francisco International Airport, San Francisco, California, February 7, 2015. REUTERS/Louis Nastro

WASHINGTON (Reuters) - The U.S. Federal Aviation Administration on Tuesday proposed fining United Airlines UAL.N $435,000 for operating 23 flights in 2014 with a Boeing 787 that the government alleged was not in airworthy condition.

The FAA alleged that in June 2014, United mechanics replaced a fuel pump pressure switch on the Boeing Co BA.N aircraft but failed to perform a required inspection before returning the aircraft to service. A United spokesman said, "The safety of our customers and employees is our top priority. We immediately took action after identifying the issue and are working closely with the FAA in their review."