I do not think that airplane manufacturers will openly advertise with this possibility like: 'This Boeing767 is equiped with a home run system!!'.
So, let's get this straight.
In your version of the Truth
every Boeing is fitted with remote control, but all the people who build and maintain airplanes for Boeing are keeping quiet about it. Boeing, who wish to make a profit, have fitted this expensive safety feature without it being mandatory and without advertising it. And, apparently, without patenting the system.
As has been explained to you, the pilots can if necessary literally wrestle control from the autopilot, so this would have to be an entirely separate system.
You also require that this system has never been used legitimately to thwart hijackers, since that would kinda give the game away. Apparently the one time it's ever been employed was on 9/11. Bit of a waste of money, wasn't it?
Note that the system would be
completely useless in every normal hijack situation (i.e. every hijack ever with the exception of the 9/11 attacks) because the key to a hijack is that you have the passengers as hostages. Just as they can say to the pilot: "Take this plane to Libya or we start offing the passengers" they could say that to the people on the ground, it would make no difference.
And you have not the slightest shred of evidence that any such device has been
designed, let alone built, tested and employed.
But you need it to exist for your version of the Truth, so hey presto, there it is.
And then you can say: "Well, it
coulda happened".
Yes. Alternatively, maybe secret Freemason researches into telekenesis allowed them to control the planes using only the power of the mind, amplified by special equipment recovered from the Roswell crash. But without any evidence, it is hard to take this conjecture seriously.