No phone service in these remote islands and secondly you're assuming that A-the passengers are still alive and B- the hijackers haven't collected all the iPhones, that's assuming the plane hasn't crashed. As far as fuel, obviously there would be reloading capacity wherever they planned for it to land. I have a friend who travels to those countries a lot he says the airport security in Malaysia is virtually non existent. Never underestimate these terrorists. Remember how coordinated and sophisticated the 9-11 attack was. All these planes hijacked simultaneously and flown into buildings at the same time.
I somehow still doubt that the plane made it to land. I'll bet investigators are going through and conducting extensive background checks on all names on the passenger list, including flight attendants and especially the pilot and co-pilot.
Let's say a big group of terrorists boarded this plane, like 20, and two or three of them were pilots. They take control of the cockpit, incapacitate the pilots, take control of the plane and destroy all on board communication capability including all cellphones. The new pilots then turn off the transponders and fly the plane to a predetermined landing area. Phase one of the plan is complete.
I truly hope that I'm wrong, but then again I feel for the passengers and their families if its a crash. For the record, my cousin died on Pan Am flight 103. No was very close to him. So I am a relative of a crash victim. His body was found still in the chair stuck on a tree. Very sad.