NEW YORK (CNNMoney.com) -- The tarmac rule imposed earlier this year seems to have had the desired affect -- with only one delay exceeding three hours in the entire month of August, said the U.S. Department of Transportation on Tuesday.
A United Airlines flight that languished on an airport runway for more than three hours on Aug. 5, is the only one in August to break the rule, DOT said. The rule requires a flight to deplane after it sits on the tarmac for three hours.
Last year, 66 flights sat on runways for at least three hours in the month of August, according to the DOT. The department added that the new rule has had no impact on cancellation rates in August, with the rate of 1% unchanged compared to the prior year.
The tarmac rule has been broken eight times since it was imposed earlier this year on April 29 through the end of August, according to the DOT. That's compared to 529 runway delays exceeding three hours, during the same time period in 2009.
"With the summer travel season behind us, it appears that the rule is working as planned," said U.S. Transportation Secretary Ray LaHood.
Rahsaan Johnson, a spokesman for United Continental Holdings (UAL), a merger that includes the former United Airlines, said the Aug. 5 delay occurred during a flight from San Juan, P.R. to Washington Dulles International Airport.
He said the flight was diverted to Richmond, Va. because of a thunderstorm. It could not deplane because the ramp was closed and the process of getting it off the ground took longer than three hours, he said.