Federal officials fined United Airlines $130,000 for failing to notify passengers that they could exit a plane that was delayed in Chicago for nearly five hours.

The fine is the result of federal regulations that require airlines to give passengers on international flights the opportunity to leave a plane that is delayed on the tarmac at least four hours. For domestic flights, passengers must be allowed to exit before three hours have elapsed.

If the delayed plane remains parked at the gate, airlines must give passengers the opportunity to exit every 30 minutes.

The United flight, departing Chicago's O'Hare International Airport for Tokyo's Narita International Airport, May 7, pulled away from the gate at 12:28 p.m. but returned nearly two hours later because of mechanical problems. It carried 357 passengers.

The doors to the plane were opened for 45 minutes starting at 2:25 p.m. but were closed again for more than two hours until the flight was canceled at 5:22 p.m. because of further mechanical problems, according to the U.S. Department of Transportation.

The federal agency said United failed to announce to passengers that they had the right to leave the plane.

In a statement, the airline said: “We are committed to complying with the tarmac delay regulations, and we continue to improve our procedures.”