We used a Hitec Flash 5X as master with a Futaba 6XAS as student.
We did have to buy the Hitec "one way" trainer cord
http://www3.towerhobbies.com/cgi-bin...?&I=LXN740&P=0
The Hitec master was turned on, the Futaba student was not turned on.
< edit > I'm re-reading your post and Ken's reply.
Which transmitter is controlling the plane? Hitec? Futaba?
No matter what, only the transmitter that is controlling the plane should be turned on.