Q - Is it possible to plunge a plane like the 777 into the ocean without leaving any debris behind? Low speed/low altitude then 45º plunge?

Back to our regularly scheduled programming...

So if our hypothetical bad guy used altitude excursions to disable everyone in the back, why did the airplane fly on for hours and then vanish? What was the point of it all then? Maybe just an unbalanced individual like what was alleged in the case of Capt Button? But if there was a rational motive (terror, theft of cargo) then why didn't it happen?

A flight 91 scenario is possible but it seems it would have happened much sooner, if at all.

How about this...someone in the cockpit could survive in the high flight levels ONLY if he used the appropriate setting on the oxygen mask, and used it properly. But any little mistake in that and the perpetrator would find himself disabled before he knew what hit him. Also...if he flew above the 30's the mask would NOT protect him from the bends unless he had pre-breathed pure O2 long enough to purge all the N2 from his body. He wouldn't have had time to to do that, even if he knew he needed to. Perhaps the perpetrator inadvertently took himself out along with the pax during that altitude excursion, and then the plane flew on AP following whatever route the perp had programmed until it ran out of gas.

You would have to land the plane like Sully and then let it sink intact.

Any sort of impact would break up the plane and release all sorts of debris, much of which would float.

But that's mostly irrelevant...it's a very, very big ocean and wind and waves would quickly disperse any debris such that you would not be able to spot a defined debris field.

According to the airline, totally not authorized. If that actually happened in flight, somebody is getting fired soon. The pics I saw on the media looked like they were taken on the ground.

Understood - wondering if whoever was in command of the plane may have ditched at a pre-determined rendezvous point, then sunk the plane. But that would require extraordinary skills, to land in open ocean w/o breaking apart/cartwheeling.

Happened inflight.

Malaysian MH370 co-pilot entertained teenagers in cabin on earlier flight | World news | theguardian.com

Almost impossible to pull off reliably in the open ocean, in all normal conditions the sea state would be too high. Sully lucked out with a calm, smooth conditions on an inland waterway.

But why would you even want to land it in the water?

Assuming the news are right (BIG if) whoever did this had a preconceived plan, as data appears to show a fairly clinical execution of twists and turns to silence comm and get out of Malaysian airspace. The scenario is possible only if the perp didn't have in-depth knowledge of oxygen levels.

Not to beleaguer this angle but to answer the question. Most events have a human element, and there are two broad scenarios here - either it was accidental, or it was purposeful. Assuming the latter, then there must've been a reason to make the plane completely disappear w/o a trace. If the purpose was to get attention/make a point, if the plane is never found would go down in history as one large unsolved mystery. But as you pointed out, time and currents would disperse debris, so landing it in water is a moot, unless whoever did it was planning on surviving and being picked up somewhere. Looking at the problem from the mind of whoever did it instead of looking at the (potentially incorrect) data points we are getting. Thanks for the insight though.

All of my speculation is bound by human motives. Consider a motive and then consider the technical feasibility of fulfilling that motive. Assuming it's purposeful, which it's really starting to look like at this point.

I can't see a motive to land on the water, anyone with a enough piloting skill to even try it would know it's probably not going to work out in a big jet.

Random technical failures have no motive and this are harder to predict and analyze, especially with little or no data.