Hmmm, the skin is still in the MiG-29.nif file, not the dds.
Also, the model is certainly awesome but it's 20,000+ polygons. Having a few of these in the game will make the game unplayable for most people. You should significantly reduce the polygon count. It's best if you could make it below 2000 polygons, but for something like planes, that usually don't appear in large numbers at once, you could probably get away with 2000-3000 polygons.
The best place to start with the polygon reduction would be to just reduce the detail on all the round/cylindrical parts. At the kind of distance and scale that units appear in civ4 an 8-sided cylinder looks as good as an 18-sided one but performs three times faster.
Second good place to look would be the various places on the plane that are not easily accessible/visible. Simplest example is the bottom part of the plane. Basically most of the time you don't even see it, so you could significantly reduce the detail there. You could certainly remove the various "detail" pieces there, such as nozzles, any landing gear components, etc. Rockets can also be made very simple - 6 sided cylinder as a base for a rocket is more than enough. Also, a place like the inside of the exhaust ports - it just needs an inverted 6-sided cone, any more than that and you're wasting polygons on something that most people will never even notice.
I know it's difficult to reduce polygons so much, especially on a model you put so much work into, but many people that play civ4 aren't even gamers in the traditional sense and don't have very powerful rigs, and you don't want to exclude them - I mean a pissed off strategy genious that have taken over the world on deity difficulty countless times, who knows what kind of havoc they could cause