Can a commercial airliner sink to the bottom of the ocean?
Can a large modern jet airliner plunge intact underwater from flight?

No.

Large airliners are not desgned for this and are not even strong enough to make a landing on water in less than perfect conditions.


E.g. 961

striking the surface at a larger angle would certainly lead to widespread disintegration.

Is it possible for a large modern jet airliner to sink intact?

Yes (as near as makes no difference)

Almost all large aircraft impacting the sea surface in an emergency or uncontrolled will break up immediately and catastrophically.

One notable exception was US1549, an A320, which was landed on water without breaking up. It was described as "still virtually intact though partially submerged and slowly sinking". The left engine detached and sank.



So a controlled landing on water is possible under extremely favourable circumstances. It would then be possible for the aircraft to sink in more-or-less one piece without creating a large amount of floating debris.