Black hat thief got his controls overridden by the white hats, who then ditched the plane where it could do the least damage?
A possibility too. I mean, who would have a better view of the plane's position than the F-15 pilots behind him.
The so-called hijacker was too calm and scripted, but who knows what goes through someone's mind when they're fixing to pull their own plug. Possibility of medicinal help too, though he didn't sound intoxicated at all. So it wasn't like booze, pot, or any hallucinogen. IMHO.
Thought it crashed on land? Had many opportunities to get it in the water if remote control was possible.