Per above correct you can only bind a controller(s) to one active aircraft/drone at a time. Otoh, an aircraft can have multiple controllers bound to it at the same time (one primary active). Note livelink count as a controller. For example, Ctrl-A is the primary, Ctrl-B is a livelink, Ctrl-C is a second controller also bound being used in "teaching/training" mode, all are bound to Aircraft-A. To use with Aircraft-B, rebind the controllers (and livelink) to Aircraft-B.
Ctrl-A <---> Aircraft-A
Ctrl-B <-------+ ^
Ctrl-C <- - - - - - +