United operated plane not in 'airworthy condition' 23 times, FAA says

PHOTO: Crew members greet a United Airlines Boeing 787 Dreamliner at OHare International Airport on May 20, 2013 in Chicago.PlayScott Olson/Getty Images
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The Federal Aviation Administration is threatening to fine United Airlines $435,000 for operating a jet that was "not in an airworthy condition," the agency said.

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According to the FAA, United mechanics replaced a Boeing 787's fuel pump pressure gauge on June 9, 2014, but did not inspect the work until 19 days later.

In the interim, the plane made 23 domestic and international passenger flights, including two after the FAA notified United of the lapse, the agency alleges.

"We immediately took action after identifying the issue and are working closely with the FAA in their review," United told ABC News, adding that safety is the airline's "top priority."

"Maintaining the highest levels of safety depends on operators closely following all applicable rules and regulations," FAA Administrator Michael Huerta said in a statement. "Failing to do so can create unsafe conditions."

ABC News' Whitney Lloyd contributed to this report.