But planes are designed to survive water landings, and a skilled crew can use those design elements to keep a ditched aircraft afloat and the passengers safe, according to Bill Waldock, a professor of safety science at Embry-Riddle Aeronautical University in Prescott, Ariz.
"You've heard of airworthiness," he said. "Planes are also designed for crashworthiness."
Waldock, who is also a pilot and an aircraft accident investigator, said planes, like ships, will float "as long as you don't let the plane get full of water. It's the buoyancy provided by the air in the plane."
In this case, the plane that went down Thursday was an Airbus 320, which has a low wing. This allowed most of the fuselage to remain above water, contributing to the aircraft's buoyancy, he said.
Waldock said the escape slide that is sometimes used to evacuate passengers from planes on tarmacs can also double as flotation devices for aircraft, as it did Thursday.
But he emphasized the skill displayed by the crew in that operation, starting with the pilot.