Generals Alpha is an OpenRA mod that recreates Command & Conquer: Generals on OpenRA engine as much as possible but using Red Alert and Tiberian Dawn artworks.
Countermeasures upgrade didn't do the main thing it is supposed to do before in GenAlpha, it just adjusted the armor for the aircraft, which was just a secondary effect in the original game. Thanks to dnqbob, now the Aircraft actually leave flares for the missiles to deflect them when the upgrade is researched.
Flare Artwork is from Bdragon1727.itch.io