U.S. airlines could face stiff fines for stranding passengers aboard grounded planes for more than three hours, according to a regulation that officials said on Monday was aimed at upholding passenger rights.

The Transportation Department initiative tries to address public and government frustration with lengthy runway delays, especially those that leave passengers without food, water or adequate bathroom facilities.

"Airline passengers have rights, and these new rules will require airlines to live up to their obligation to treat their customers fairly," Transportation Secretary Ray LaHood told reporters.

For the first time, the government will require airlines to let passengers get off planes that have been at a gate or on a taxiway waiting to take off or get access to a terminal.

Exceeding the three-hour limit could result in fines of up to $27,000 per passenger, the Transportation Department said.

Airlines also would have to ensure that passengers get food, water and adequate bathroom facilities during long delays.

There were 1,100 tarmac delays of at least three hours between October 2008 and October 2009, government figures show. There were more than 7 million flights during that period.

In November, the Transportation Department proposed $175,000 in fines against Continental Airlines Inc, its ExpressJet Airlines affiliate and Mesaba Airlines, a unit of Delta Air Lines, for a nearly six-hour ground delay at Rochester, Minnesota, in August.

Overall flight delays cost U.S. airlines roughly $9.8 million in 2008, according to industry figures.

Shares of most major carriers were up slightly on Monday despite significant weekend cancellations and delays due to the Northeast snowstorm and higher oil prices. Analysts have been more positive about the sector recently.

The decision to let passengers off planes rests with the captain, who could exceed the three-hour limit because of security or safety concerns. Crews could also keep people aboard if letting them off would disrupt air traffic.

The regulation would take effect just at the start of the spring and summer travel season, the worst for delays.

Major airlines, through their trade association, said they would comply even though they say it will lead to more canceled flights and more passenger inconvenience.

"The requirement of having planes return to the gates within a three-hour window or face significant fines is inconsistent with our goal of completing as many flights as possible," said Jim May, CEO of the Air Transport Association.

Airlines have fought congressional efforts to craft similar rights legislation. Two lawmakers leading the attempt, Senators Barbara Boxer and Olympia Snowe, applauded the administration's regulation. But the pair said they would push ahead with their bill to put requirements and penalties into law.

The rule, tougher than one proposed by the Bush administration a year ago, also prohibits airlines from scheduling chronically delayed flights. Continuing to do so could result in fines. It also requires airlines to display flight delay information on their websites.

The regulation does not apply to international airlines. Most cases involve domestic airlines.

Kevin Mitchell, chairman of the Business Travel Coalition trade group, said airlines must reevaluate scheduling practices at busy airports, especially in New York. "Over the long term, however, passengers will move throughout the aviation system much more efficiently."