The three judges expressed skepticism that states should be allowed to impose such a law on an industry already subject to extensive federal oversight. It was likely, they implied through their questions, that federal authority would pre-empt state laws on the issue.

New York's law requires relief for people who have been trapped in a plane on the ground for at least three hours. It was passed after passengers at Kennedy International Airport were stranded on planes for more than 10 hours with no food and overflowing toilets.

The court did not immediately rule on the constitutionality of New York's Airline Passenger Bill of Rights.

The judges said they were sympathetic to the needs of passengers on planes, but they seemed to agree that only the federal government can regulate airline services.

Judge Brian M. Cogan said New York's law might lead to multiple solutions by states nationwide that would subject airlines to all kinds of requirements.

Judge Debra Ann Livingston agreed.

"There is a patchwork problem in that every state should be concerned about this and probably would write different regulations," she said.

Even though the judges had not yet ruled, Judge Richard C. Wesley defended their apparent stance.

"This is a pre-emption issue. Judges aren't heartless people in black robes. Three judges must decide whether New York stepped over the pre-emption line," Wesley said.

The law was challenged before the appeals court by the Air Transport Association of America, the industry trade group representing leading U.S. airlines.

Seth Waxman, a lawyer for the trade group, told the judges that a dozen other states were considering laws similar to New York's law. He said Congress was considering its own legislation.

"If regulation is required in this area, it must be national to avoid what otherwise is a patchwork solution," Waxman said.

Barbara Underwood, arguing in defense of the law, said it required minimal standards and protected the public.

She said planes in line for takeoff might, after three hours, be forced to return to the gate to pick up more food and water and empty its restrooms or need to summon a delivery service to perform those chores.

A recent federal report showed that about 24 percent of flights nationally arrived late in the first 10 months of last year, which was the industry's second-worst performance record since comparable data began being collected in 1995.

Kennedy airport had the third-worst on-time arrival record of any major U.S. airport through October, behind the New York area's other two major airports, LaGuardia and Newark, according to the report.

Wesley called it a health and safety issue.

"What it really is about is human dignity," Underwood said.

Queens Assemblyman Michael Gianaris, a Democrat, the prime sponsor of New York's Airline Passenger Bill of Rights, said after the arguments that he was not discouraged by the questions posed by the judges. He said he would welcome a national law protecting airline customers.

"I'm hopeful the judges will preserve the law," he said.