Geez, people, you don’t need to jam the cellphones—they don’t work onboard!
The hijacking begins with BOTH transponders being turned off, 14 minutes apart. I'm speculating on the state of all the passengers and their inability to communicate by whatever means possible. Or were they not aware of anything unusual during the flight?
If I was to steal a jumbo jet I would not be so complacent upon believing that philosophy. Cover any possibility the Evil Satan USA has some form of satellite or Predator drone nearby that can intercept even a simple cell phone call.
From a plane at 40,000 feet even.