[GuerraCivil]

I have read, that during the Winter/Continuation War Finnish Air Force planes faced very often "friendly" AA fire. As there were much more Soviet airplanes in air, the Finnish AA usually shot everything that flew on the sky. During the Winter War at least one Finnish fighter was shot down by Finnish AA and the pilot was killed (IIRC).

However, the Barking Creek Incident in 1939 as well as the Bodenplatte fiasco in 1945 are in my opinion the two outstanding "classics" when it comes to "friendly" fire in WW2.