WASHINGTON (AP) — One of Donald Trump's jets has been flying for months with an expired registration, Federal Aviation Administration records showed Tuesday.

The Republican presidential candidate's airplane lost its registered status in January after failure to pay a $5 fee to the FAA. The aircraft in violation is not Trump's Boeing 757, the renovated commercial jet that the billionaire sometimes uses as a backdrop for his rallies. Instead, it is a 1997 Cessna Citation X, a far smaller plane which Trump has used to visit smaller airports. Citation jets of a similar vintage sell for around $3 million, according to aviation brokerage firms' current listings.

The FAA declined to comment beyond confirming the registration was expired. In an email to The Associated Press, Trump campaign spokeswoman Hope Hicks said "the standard renewal process is just about complete" for the plane.

The New York Times, which first reported the expiration on Tuesday, said the registration lapse could ground the jet for days.

Plane registrations are supposed to be renewed every 36 months. If the FAA learns that a registration has expired by the plane is still being flown, the agency typically sends a warning letter to the owner, according to aircraft operators who asked not to be named because they didn't want to be associated with the Trump case. Fines are also common. They vary depending upon the type of aircraft, but are often thousands of dollars per each time the plane has been flown after its registration expired.

The news emerged as voters in Trump's home state of New York cast their ballots Tuesday in the state's crucial presidential primary.