New York: The registration of Republican presidential hopeful Donald Trump's sleek Cessna jet, which he uses to make campaign stops in the US, has expired.
The Federal Aviation Administration records show the aircraft's registration lapsed on January 31, the New York Times reported.
Laura J. Brown, a spokeswoman for the administration, said the plane's registration was not in good standing and the owner had not renewed it.
With a few exceptions, aircraft must be registered in order to fly. Trump's plane could be grounded for days, or even months, while the issue is being sorted out.
The FAA could fine or assess other penalties against the owner, the operator or both. Trump owns the plane through a limited liability company.
Though it is unlikely that the agency would seek the maximum penalty, flying with no registration could result in a civil penalty of up to $27,500, a criminal fine of up to $250,000 and imprisonment for up to three years, it said.
Hope Hicks, a spokeswoman for the Trump campaign, declined to answer several questions about the plane's registration or use, saying the renewal process "is just about complete".
As of late Tuesday, the FAA had not received a registration renewal application for the Cessna, according to Brown, the agency spokeswoman.
Trump can still fly; most candidates typically charter a private plane.
Trump has four other registered aircraft: A Boeing 757 and three Sikorsky helicopters, a fleet that has become a critical part of the billionaire's image he has sought to project on the campaign trail.
Trump often presses the 1997 Cessna 750 Citation X, which was designed to seat eight people, into action.
It has made hundreds of flights since he announced his plan to seek the Republican nomination in June 2015, according to FAA records reviewed by the New York Times.
Dozens of those flights were made after January 31, when the plane's registration expired.
The administration warned Trump that the Cessna's registration was set to expire, records show.
The registration for Trump's other aircraft and three helicopters are current, records show.
Registering an aircraft is cheap: It costs only $5, and the registration is valid for three years.