Hi Ouldy1 and Hubert,
Thanks for the kind replies. I can see now where my reading of the manual went wrong: On page 72 it says under 'Strategic Bombing', 'Fighters, Tactical Bombers, Bombers and Carriers can attack resources...', two paragraphs down it then says, 'Bombers can inflict damage on resources even if there is a unit positioned on top of them.' I read this as, 'All of the above can inflict damage on resources even if there is a unit positioned on top of them.' Taking 'Bombers' to mean Fighters, Tactical Bombers, Bombers and Carriers.
What you are saying so (and the manual too :-) is that only Bombers attack the underlying resource if it has a unit on top of it. Fighters, Tactical Bombers and Carriers attack the unit on top of the resource.
One more question about this: What about Medium Bombers? I'm looking at turn 1 of the '1939 World War' scenario in 'Assault on Democracy' and attacking Krakow with the Medium Bomber on grid (182, 75) this seems to only attack the unit. Medium Bombers act like Tactical Bombers in this regard then? Is that right?
Thanks for your time guys!