ah, okay. right, alien bases, I totally forgot about them
I think the "one check every 30 minutes" is kind of overly simplified, though... just imagine: an interceptor can fly immediately next to an UFO for almost half an hour and never see it, because it came into his radar range after the last check and flew away before the next one.
I think that's not what we want, is it? It might be how it was done in the original, but perhaps only for lack of a better way, because this way saves some CPU time.
I would like to suggest changing the mechanic for craft radar to more frequent but less reliable checks. perhaps every 5 minutes with a chance of 25 percent?
(btw, what's the radar range of aircraft? is it the same for every craft?)
I would also like to suggest changing the mechanic for base radar to "more radar facilities shorten detection intervals" instead of "each radar gets its own check".
I know this changes a more-or-less fundamental game mechanic, but really, in this case the original mechanics suck big time