One evening in May, passengers boarded United Flight 661 from Newark, New Jersey, to Chicago. As the plane readied for takeoff, a thunderstorm swept in, grounding the plane. The storm, which produced winds upwards of 50 miles an hour, was fast moving and cleared a few hours later. And yet, seven hours after Flight 661 first left the gate, it was still on the tarmac, passengers crammed inside. Around midnight, the flight was canceled. More and more travelers across the United States are coming ho