Methods for two people to communicate without being noticed

[LSLGuy]

Kinda like this then, but more successful:

Almost 100% Foolproof way to Cheat in Exams?

I thought I’d told this story before but I can’t seem to find it. My class at USAF pilot training included two Saudi Arabian student pilots. One was a real gentleman, a high quality guy. The other was a useless fatcat frat boy. Both had pretty good English; plenty enough for the job at hand. Each day began with all of us sitting in a classroom. An instructor would explain an inflight emergency scenario then call on somebody to respond. If you were called the drill was to leap to attention,…

You might find some other inspiration in the other posts of that thread. Not solving the same problem, but a related one.