Yeah, I only brought this up with the idea of implementing it in my WWII scenario -- so: very specific use here. Linking aircraft types to techs is fine up to a point, but in some cases, I hate see early jets and other 1944 aircraft showing up in 1943... so for some of these aircraft types, there needs to be both a tech and a year requirement governing their availability. This is more of a flavor thing than a absolute technical thing.