About 140 rail passengers heading to or from Kennedy International Airport were stranded for hours on Saturday evening and had to walk beside the tracks to the nearest station, after a computer malfunction caused the AirTrain system to shut down. The trains run on an elevated platform high over the Van Wyck Expressway in Queens.

The service problems began at 5:33 p.m., and service was finally restored at 10:18 p.m., according to the Port Authority of New York and New Jersey, which owns the service. In all, three two-car trains were stranded.

“It was a terrible experience,” said a passenger named Danielle, 30, who had flown in from Pittsburgh and was stranded for more than two hours as she tried to get home to Lynbrook, N.Y. “They didn’t give us any information about what was happening. Then the air conditioning shut down.” She declined to use her last name because she is a city employee and not authorized to talk to the news media, she said.

Passengers on two trains had to walk nearly a mile. Officers from the authority’s emergency response unit led the way with flashlights, and others stood at posts along the way to ask if anyone needed help.

Steven Robert Smith, who was visiting from London, said the train’s public address system told passengers only that they would be moving shortly, and later, that agents were on the way. But none arrived, he said.

Tensions mounted, and soon, the temperature in the train did the same.

Mr. Smith said he pushed an emergency intercom button to get information, “but even after repeatedly pressing, nobody would speak to us. It was now getting warm, and near an hour and a half of waiting.”

Steve Coleman, a Port Authority spokesman, said that personnel from Bombardier Inc., which built and operates the AirTrain service under a contract with the Port Authority, handles such calls, not Port Authority employees. The complaints about a slow response and inadequate communication echo similar criticisms directed at the Metropolitan Transportation Authority after the blizzard of December 2010, when riders on an A train were stuck for hours because the authority “forgot about” them, as the president of New York City Transit, Thomas F. Prendergast, admitted in a City Council hearing last year.

Mr. Coleman said “as soon as we became aware that there were stranded passengers, we dispatched Port Authority Police to evacuate them from the trains.”

The computer malfunction was eventually traced to a loose wire in the main computer, Mr. Coleman said. The AirTrain carries 50,000 riders each day, he said.

Mr. Coleman said that Bombardier did not tell the authority that trains were stranded until an hour and 45 minutes after the problem started, “which goes against the protocol.”

The authority then sent its police officers to evacuate the trains and dispatched 19 buses to replace the train service, Mr. Coleman said.

Joseph Osterman, director of operations and maintenance for Bombardier, said he spoke with the Port Authority a half-hour after the shutdown, but did not know what time he told the authority that trains were stranded. He also said the company was still looking into what messages were communicated to passengers.

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