At first I thought with the number of people with cellphones on the plane someone would call for help. But then I remembered there are electronic devices which disable cell phones ability to make/receive calls that are readily available and cheap.
I think a bigger problem is that cellphones go out of range. Once they are off-shore, and 20 or 30 miles from a celltower, they do not work.
Some have commented on how phones worked during 9/11. That’s not relevant here, because the 9/11 plane paths were entirely over land, where cell towers are plentiful.
Is it possible to jam the transponder signal without actually turning off the equipment?
If the plane was over the ocean when it went to 45,000 feet (IMO as part of a plan to decompress the cabin and kill the passengers), the plane would have been out of cell phone range. I think this was a sick but well-conceived theft of the plane by either the pilot, co-pilot or a crew member who had access to the cockpit.