Mr. Hennessey wondered if La Guardia had a shuttle bus to take passengers to the terminals — not just the Marine Air Terminal (officially Terminal A) but to Terminals B and C.

There is a shuttle, Mr. Dupoux said, just as there are shuttles between the terminals at Kennedy and Newark Liberty. “But it is not 1, 2, 3,” he said. “You have to wait.”

That would not be the only wait if the proposed train takes shape. The Transport Politic, a website dealing with urban planning and public transportation, said the AirTrain would not save time; in fact, travel times to destinations like Grand Central Terminal and Yankee Stadium “would be longer for passengers using the AirTrain than for passengers using existing transit services.”

Back in Mr. Dupoux’s car, the consensus was that airport trips take longer these days. Mr. Dupoux said that when Eastern was still in business, in the mid-1980s, it took 20 to 25 minutes to drive from Kennedy Airport to his sister’s house in Elmont, on the Queens-Nassau County border. “It was about the same from La Guardia,” he said. “Now it’s 30 to 40 minutes. You’ve got more cars on the road and more construction.”

Mr. Dupoux suggested a dedicated highway lane, like the high-occupancy vehicle lanes on the Long Island Expressway. The one he had in mind would run from the Robert F. Kennedy Bridge (originally the Triborough Bridge) and would have only two exits — one for La Guardia, the other for Kennedy.