Passengers on board the ill-fated tourist helicopter that crashed Sunday in New York City may have drowned because they couldn't unfasten their safety harnesses. The chopper plunged into the East River after pilot Richard Vance made a "mayday" appeal for help, citing engine failure. All five passengers died, and Vance survived. The doors to the Eurocopter AS350 were open so passengers could snap photos. But when it went down, the open doors allowed the interior to fill quickly with water.