All it takes is one phone to be on, regardless of human intervention. I would wager someone forgot to turn their phone off. Nevertheless, if the flight was hijacked and the hijackers were pros, as they clearly must be, they might have had a cell jammer. Regarding IMEIs, cell numbers of passengers, and tower logs, well that's what we have all those 3 letter acronym agencies for. I'm sure they haven't just been sitting around all this time. I don't think it's just the navy and air force sending search and rescue.