The transport with the para, will be fired by any existing AA guns in the enemy territory , when flying over it without conducting an air assault or being a part of a combined ground and air assault but only once, I think you will need to declare an air assault or just say you flying over the territory. I can see tho AA guns firing twice a turn, first when enemy planes fly over it through the territory where AA are in, conducting a strategic attack, and second if the territory the AA are in gets attacked they can be used as a front line unit or as AA if the enemy has planes supporting his attack. Rules doesn't say anything about AA firing only at one target so I read it as you can,?