WASHINGTON – The way Kate Hanni tells it, a holiday trip that left her family stuck inside a grounded airliner for nine hours without food, running water or working toilets amounted to “cruel and inhumane” treatment that no passenger should have to endure.

So infuriated was she about the ordeal in December that she and her husband started a coalition of fed-up fliers to press for an industry-wide passenger bill of rights. Earlier this year, after JetBlue’s cancellations of hundreds of flights that stranded thousands of passengers, their cause caught the attention of lawmakers on Capitol Hill.

On Wednesday, the Napa, Calif., resident appeared before a Senate panel to lend support to a bill by Sens. Barbara Boxer, D-Calif., and Olympia Snowe, R-Maine, that would create a federally mandated set of rights to supplement the voluntary guidelines airlines follow now.

“This winter’s events make clear that the airlines have failed to live up to their promises and it is time to literally lay down the law,” Boxer said during at the first hearing on the bill by the Senate Committee on Commerce, Science and Transportation.

The measure would allow stuck passengers to get off an aircraft after three hours on the ground, unless the pilot believes the plane soon would be cleared to depart or if letting passengers off would compromise safety. The bill also would require airlines to provide food, drinking water and adequate restroom facilities.

The legislation’s requirements are, its sponsors say, “a modest approach” that would impose little hardship on airlines, which are still recovering from the downturn in travel after the Sept. 11, 2001, attacks.

“The time has come to at least demand a reasonably based position,” Snowe said. “People make a significant investment … in purchasing a ticket, not to mention the cascade effect that (a delay) has – whether it’s their vacation plans or it could be a family emergency, whatever the case may be. And I think there’s no accountability.”

Rep. Mike Thompson, D-Calif., has introduced similar legislation in the House.

Calvin L. Scovel III, the Transportation Department’s inspector general, stopped short of endorsing a legislated passenger bill of rights but did tell lawmakers that airlines need to do more to improve customer service. A 2006 audit by his office found that only five of the 12 airlines that had signed on to a voluntary 1999 customer service commitment had systems in place to meet their promises – including seeing to passengers’ essential needs during delays.

Airlines oppose mandated customer-service requirements. James C. May, the president and chief executive officer of the Air Transport Association of America, a trade group representing major airlines, pointed out that hours-long delays are relatively rare and warned that the proposed legislation could lead to further delays and cancellations. He said market forces, not Congress, ought to dictate how they treat their passengers.

“Following safety, on-time service is the most important factor for success in the airline business,” he testified. “The reputations that the airlines earn for good service is the currency they have to offer in the marketplace.”