Story highlights "The chances of not having any debris on top of the water is very remote," pilot says

An in-flight breakup would scatter wreckage; a steep plunge would still leave some behind

Hitting water from high altitude is "like concrete," pilot says

Could it all have sunk?

So far, of the possible pieces of debris spotted from the air or from satellites, none have turned out to be from Malaysia Airlines Flight 370. But it's extremely unlikely that the Boeing 777 would have slipped beneath the waves intact, and if it had broken up, pieces of the aircraft are likely to have been cast adrift on the surface, said Jim Tilmon, a former American Airlines pilot and aviation analyst.

"The chances of not having any debris on top of the water is very remote," Tilmon told CNN. But the amount of flotsam left behind in the crash would most likely vary based on how the plane -- now believed to have been lost in the Indian Ocean west of Australia -- hit the water.

An in-flight breakup would have scattered wreckage over a wide area, Tilmon said. If the jet hit the water at a steep angle, at high speed, it would likely have taken much of its frame and contents down into the deep with it.

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That's what happened when a Seattle-bound Alaska Airlines jet plunged into the Pacific Ocean off California in 2000, killing all 88 aboard.

Even in such a case, however, numerous pieces such as seats or luggage bins would likely have broken loose and bobbed to the surface, Tilmon said.

"It's not like striking your hand into the water. It's like slamming your car into a brick wall," he said. "And that's the more likely result of that kind of situation -- you're going to have lots of debris."

A less steep angle -- even an attempt at a controlled descent -- might be more forgiving to the frame of the 200-foot jetliner. But when the pilots of a hijacked Ethiopian Airlines flight made an emergency landing in in the Indian Ocean off Africa in 1996, the Boeing 767 still broke apart when it hit the water, killing 125 of the 175 people aboard.

"Remember, water is like concrete," Tilmon said. "So you hit it hard enough, it destroys the airplane's integrity. And you can have pieces that are going to be there, and open up things like compartments and sections of the airplane that have items that will float."

The most successful water landing in recent history was the so-called "Miracle on the Hudson" in 2009, when the crew of a crippled US Airways flight landed safely on the river off Manhattan after losing both engines. The Airbus A320 remained intact, and all 155 passengers and crew made it safely off the aircraft.

But the Hudson is "pretty relaxed by comparison" to the remote Indian Ocean, "where you have swells of 10, 12, 16 feet," Tilmon said. "It's pretty difficult to make that kind of landing on water."