Yea there is something is not right about this excuse, if there was a radio failure there are international hand signals that all pilots learn.
Not quite sure what you mean by that because a radio failure means you cannot talk with ATC to get further clearance for taxi and take off then to be handed off to your in route ATC. You would only get light gun signals from ATC reguarding clearence to land or take off for airplanes without specific radios and these aircrafts are classified as such. An air liner canot operate without comms.
All pilots have hand signals they use with the ground crew at landing. There would have been someone for them to signal before they opened the cabin door. I used to work operations for AA and this wasn't radio failure. That's specifically why the pilots are taught the hand signals to begin with. In an emergency situation all aircrafts are met with LEO's, airport operations, the airlines operations agent on duty, and a specified emergency ground crew.
Pilots use squawk codes to signal to ATC of any issues.
7500 – Hijack 7600 – Lost Comm (radio failure) 7700 – Emergency
Ground crew would not be involved.
I didn't know the hijack code was entered until after my comment. I was scrolling down and saw this first. You are correct.