I play standart map. I was the leading faction. I get air power, started slowly conquering bases. I have around 10 planes. Randomly game throws me to desktop. I load the save file, but it crashes at the same point, on AI turn. That happens with 4th and 3rd difficulty. Before that i finished games on 1-3 levels. It did not crash.

Is there population or unit count limit? Anyone had this issiue?

sorry, I played smac gog version. Vanilla game.

If you share the save file I can give it a try here, see if I reproduce your crash.

The unit count limit is 2048. If you encountered it (I never did), I believe the game would prohibit you from making more units. The only way to bypass it would be an old version of Scient's unofficial patch; because it caused crashes, the limit was restored in later versions. It would be very unlikely and silly for you to have gone out of your way to find and download this old version.

What you could try doing is downloading a newer unofficial patch.

The unit limit can now be increased on Thinker Mod with the more recent builds, more information here. It also fixes numerous bugs and most likely the one OP is referring to.

There is no other way of increasing the unit limit, Scient's Patch does not implement this change even though some documentation may claim otherwise. If you use the older patch it might just cause game crashes since that change should not have been included there.