Sometimes AI planes at the start of the flight scene are untargetable unless you get atleast 3 miles away from them. This usually happens when you add a new plane for them to fly around or when editing and saving existing AI friendly planes.

When you group the AI planes in one name group, the AI will spawn the first plane in that group more frequently than others. (in my case I use z-AI- [unique name] so all of them will stay at the end of my plane list.)

these big designs (plane 1 and plane 2) just doesn't show up even if they are clearly within the 7 wings, 150 total parts limit. I even deleted everything in the AircraftDesigns folder except these two so they are the only ones that will show up. but it still doesnt happen. Somehow I manage to get Plane 1 working for the AI by changing its main cockpit to a regular sized one but Plane 2 still doesnt show up on Sandbox no matter what I do.

and the Plane list doesnt update itself when saving planes while it is open. you would have to open it again so it would show the design you just saved

Behold the Invulnerable AI Enemy i shot this guy two times with guardian missiles and it is still ALIVE!! first shot took out its Vertical stabilizers and one of its horizontal stabilizer. the second shot took out its remaining stabilizer. I killed myself in a missfire (my own guns hit my plane) when trying for a third shot.