The most sensible conclusion i have heard is that if a pilot detects smoke in the cockpit then he will head to the nearest airfield that can take the aircraft. All good pilots know where the nearest one is at all points. If they have turned to the nearest strip (which was in the direction they think it finally headed) and then been overcome by smoke (become unconscious) then they would have just flown until its run out of fuel.
I hope they find it in what ever form so that people can be either repatriated or re-united. Conspiracy theories are always interesting to read though.
And Diego Garcia cant be that "secret" when they had a royal navy person filming there for the millie awards in december
