Airlines face three-hour limits for how long they can hold passengers on stranded airplanes under new U.S. regulations. (Associated Press)

U.S. airlines will be forced to let passengers leave airplanes stranded on the tarmac for more than three hours, under new regulations that come into effect in mid-2010.

Airlines have strongly opposed a hard time limit on tarmac strandings, saying that forcing planes to return to gates so that passengers can get off could cause more problems than it cures. They predict more flights will be cancelled, further delaying passengers from reaching their destinations.

From January to June this year, 613 planes were delayed on tarmacs for more than three hours, their passengers kept on board.

Under the new regulations, set out by the U.S. Transportation Department, airlines operating domestic flights will be able only to keep passengers on board for three hours before they must be allowed to disembark a delayed flight. The regulation provides exceptions only for safety or security, or if air traffic control advises the pilot in command that returning to the terminal would disrupt airport operations.

Airlines will be required to provide food and water for passengers within two hours of a plane being delayed on a tarmac, and to maintain operable lavatories. They must also provide passengers with medical attention when necessary.

Airlines that violate the coming regulations could face fines of up to $27,500 US per passenger.

"Airline passengers have rights, and these new rules will require airlines to live up to their obligation to treat their customers fairly," U.S. Transportation Secretary Ray LaHood said in a statement Monday.

Airlines fined

Last month, the department fined Continental Airlines, ExpressJet Airlines and Mesaba Airlines a total $175,000 US for their roles in a nearly six-hour tarmac delay in Rochester, Minn. On Aug. 8, Continental Express Flight 2816 en route to Minneapolis was diverted to Rochester due to thunderstorms.

Forty-seven passengers were kept overnight in a cramped plane amid crying babies and a smelly toilet because Mesaba employees refused to open a gate so that they could enter the closed airport terminal.

The case marked the first time the department had fined an airline for actions involving a tarmac delay. Transportation officials made clear the case was a warning to the industry.

Consumer advocates have been pressing the department and Congress for at least a decade to do something about extended tarmac delays. However, past efforts to address the problem have fizzled in the face of industry opposition and promises to reform.

Congress and the Clinton administration tried to act after a January 1999 blizzard kept Northwest Airlines planes on the ground in Detroit, trapping passengers for seven hours. Some new regulations were put in place, but most proposals died, including one that airlines pay passengers who are kept waiting on a runway for more than two hours.

The Bush administration and Congress returned to the issue three years ago after several high-profile strandings.

In December 2006, lightning storms and a tornado warning shut the Dallas-Fort Worth airport, causing American Airlines to divert more than 100 flights and stranding passengers on some planes for as long as nine hours.

Two months later, snow and ice led JetBlue Airways to leave planes full of passengers sitting on the tarmac at New York's Kennedy International Airport for nearly 11 hours.