Planes, like the Airbus 320 which made an emergency landing in the Hudson River Thursday, are designed to survive water landings and a skilled crew can use those design elements to keep a ditched aircraft afloat and the passengers

"You have to understand you have compromised engines, or no engines, no altitude, no speed and no room," he said "If you look at the Hudson River, down on a boat, it looks pretty wide. When you're in the air and you see it, it's a very closed area and you have hit that ribbon of water."

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."