This is one of those claims that's kind of an acid test on whether or not a truther can think for himself. Common sense and a teeny, tiny speck of imagination is all you need to realize the "hijack code" claim is silly.
Be the first truther to answer this question please, Clayton. Why on earth would you be worried about setting the transponder(
something that does nothing at all to improve your immediate, dire situation) when someone violently breaks into the cockpit and starts killing you. Maybe it'll help to try to imagine the situation. Or perhaps you might also lookup the time it took Fedex 705's crew to send a the 7500 code in a somewhat similar circumstance. The crews were just a little too busy trying to
stay alive, and the resetting the transponder was pretty far down on the priority list.
Here's a picture of a typical 757/767 transponder control head. Walk me through sending the hijack code and explain how you can do it 1-2 seconds.