Is 35,000ft out of mobile reception? I don't fly often, but the times i have, i've never text mid flight. Can you not send a text/call at that altitude? Or does the guy turn the oxygen off, then climb up to 50, 000ft (?) to get out of range of any potential 999 calls from passengers? I suppose it's a perfect ploy this really, turn off the oxygen, by the time anyone has a clue, everyone is dead. It's actually really scary a pilot has that control.
edit, this is random, you'll probably all know this anyway. Is 911 the emergency number for america? Odd that! Right, sorry, carry on..