I’m not in front of my laptop right now, but I believe it’s called 3D Edit. It was part of the software package that came with the laptop. But, I really didn’t do much creative. Mostly I stole from sprites that were already in the game. For example, the CF-104 is just the Belgian Starfighter with Canadian roundels added by me - the camo pattern happened to match. The Nomad helicopter is actually an Alouette with rotor blades from something else - from above it looks close enough. The Cougar FSV is a MOWAG hull with a Scorpion turret stuck on top - which is pretty much what happened in reality. The Skyguard 35mm AAA is the ZU-23 chopped up a bit and scaled up with bits cut and pasted from a couple of other things. The CF-18 Hornet was a top down photo somebody took of the 1/72 scale plastic model they were building and had posted on the internet. I resized it and tidied it up a bit, added Canadian markings to it. The CH-135 I had to fiddle with, but it started as one of the single-engine Hueys already in the game that I stretched a tiny bit and faked twin engines onto the back from a three-view to make it what is more or less a UH-1N. The CH-136 Kiowa is just the AB205. The M548 is the hull from the M728 Chaparral ADS, the “pulpit” from the M7 Priest, and a canvas texture I found on the internet and resized to make the canvas top for the cargo area. The ADATS isn’t in there because I couldn’t figure out a simple way to make one - but they would more than likely have been used for defense at a divisional level, or for airfield defense, not tooling around behind a battalion of mechs and tanks, so I wasn’t too concerned about it. The hull would have come from the M113A2 or A3 - not sure how I would’ve dealt with the turret.
So, no artistic talent on my part, just borrowed a bunch of parts. Sort of like Dr Frankenstein, I guess.
Three view line drawings of aircraft that include a top view are good places to start if you can find the plane you are trying to do on the internet.