Quote:I'm going to suggest something here without many facts to back it up.  My opinion is strictly what I know regarding both technologies.

 

I'm going to guess that the "radar mode" and "transponder mode" are the means that the system uses to track and/or target an airplane.

 

"Transponder mode" doesn't always identify an aircraft as being military or civilian.  An IFF transponder broadcasts different things depending on the "mode" in question.  In general, all aircraft broadcast via IFF what is called "mode C" which mostly gives altitude information if I remember correctly.

 

I suspect that the missile targeting system is able to gather information from both.  A missile targeting system really "doesn't care" if it's a friendly or a foe.  It only wants to know where the target is and how to get to it.