United Airlines may have to fork over $435,000 to the Federal Aviation Administration after the agency accused it of flying an aircraft that wasn’t in airworthy condition almost two dozen times.

The FAA alleges that United mechanics switched a fuel pump pressure switch on a Boeing 787 to resolve a problem that a crew had noticed two days before. But the airline didn’t perform a required inspection of the work before putting the plane back into service, the FAA says.

According to the agency, the airline flew the plane on 23 domestic and international flights before it completed the required inspection on June 28, 2014.

And two of those flights allegedly happened after the FAA notified United that it hadn’t performed the inspection.

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

United wants to meet with the FAA to talk about the situation. A spokesman for the airline declined to answer questions about when that meeting would take place and about the airline’s response to the proposed penalty when contacted by The New York Times, but noted that safety is a “top priority.”

“We took action after identifying the issue and are working closely with the FAA in their review,” the spokesman said, without offering details.

United isn’t the only airline to attract the baleful eye of the FAA for maintenance related matters: Southwest Airlines was fined twice in 2015 over aircraft repairs.

And back in 2014, the Department of Justice sued Southwest for failure to pay a $12 million civil penalty it levied over improper repairs. The airline eventually agreed to pay $2.8 million to settle that lawsuit.

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