[Danae]

No idea, but that would be a very good idea, until the morons that hijack planes get a hole of the code. Have to change it month to month, or perhaps faster than that. Make it specific to each flight, known only to the Pilot before every take off. Pretty interesting idea, could save a TON of effort on the ground in chasing down wild geese.

[Jet Jaguar]

Canacian fighter jets intercept and the jet goes into halifax.

[sharktrager]

Except as the hijackers started slicing throats, I bet the pilot could be convinced to give up the code.