Chronus,
what do you make of the claims by the relatives of some nineteen passengers who have called their respective family members on the flight to hear ringing tones before their calls were cut off.
I call overseas cell phones often and this happens to me many times a year. I redial and this time the person I called pick up and confirm his cell was in his hands and never rang/vibrated. Cell phone technology is still far from perfect.
Bono,
Cell phones are only off during takeoff, people use them during flight for all kinds of activities (except calling off course).
They can only be turned 'on' in airplane mode, meaning their radio is switched off. For the network, that phone is off the grid.