Sullenberger made what ABCNews' Robin Roberts, who saw the crash from her apartment, called a "perfect water landing" into the frigid waters of the Hudson River off Manhattan.
Sullenberger is believed to have activated the plane's "ditching switch," a device that closes valves and openings on the bottom of the fuselage, preventing the plane from taking on water and allowing it to float.
"It is true the plane has a ditching switch, which closes the outflow valve and the avionics ventilation ports - in other words, those openings below what would be a theoretical float line," said Mary Anne Greczyn, a spokeswoman for Airbus.
Police, firefighters, the Coast Guard and NY Waterways ferries scooped passengers from the water just moments after the crash.
National Transportation Safety Board investigators are scouring the plane to determine if it was in fact a bird strike that led to the plane's loss of power.