OpFire Different for Heavy Bombers vs Tact/Fighters?

[GeneralPatton]

I'm the allies and have control of all the french territories and the axis have the netherlands.
I move 3 heavy bombers from Paris thru Eastern France into West Germany.  No op fire encountered even though there was an aa and fighter in the netherlands.  I try the same move with tactical bombers and fighters and both receive a message that it would result in Op fire.  Is there some rule I'm missing here?

[Joel Billings]

The Op-fire has to have a chance to hit to register. This wouldn't explain the difference unless you have super evasion heavy bombers. You can send a save to jabgamer@2by3games.com if you want and I'll see if I can figure out what's going on.