[VaSteve]

Originally Posted by Porsche-O-Phile

Sea level is very inefficient fuel-wise. It can be done but range will suffer a lot versus "at altitude" (iirc jet engines are usually optimized for FL360).

If an aircraft is slowed enough and proper techniques employed it's possible to ditch in water (Sullenburger, Hudson River). A steep descent into water at cruise or cruise-descent speed would be a guaranteed fatal outcome for everyone on board.

But could it also fly "under the radar" and land somewhere else?

I discount the cellphone thing. That makes no sense. What are people expecting to get? A busy signal? Call any cell phone that's off.