But all of this is to interrupt an ongoing mission. Is it possible to prevent or at least postpone such alien missions from spawning?
Interruption is the same as postponing in X-Com. Well, okay, you prevent them from hitting their target and spawning a mission site or collecting score, too.
In OXCE, it's technically possible to interrupt missions mid-progress by both interceptions and research completion, but implementing either is up to the modder.
But the more I know about this game, the more I feel like it is much more "race with time" type of a game and alien missions spawn probability is only affected by month number.
Well, the engine kinda supports both. But vanilla was indeed mainly time-based, and mods tend to be both time- and research-based. I might be wrong but AFAIK the air game is not a major part of progress in any major mod.
So where is the truth?
Out there?