A few notes.
Just a few notes on the game.
-Planes would not have been painted red like that, usually a green drab color. Only planes of Manfred Von Richtoven's "Flying Circus" would be painted that way.
-Bombers looked alot like normal fighters, but were typically longer or larger. They also had one tailgun that could only fire in a 45 degree angle, like this: <, above the tail, and there was a blindspot where the tailwing was. In order to shoot below themselves, the pilot had to turn the plane onto its side.
-Oberservation ballons (Your "Zepplin") were unarmed and relied on a ring of AA cannon on the ground to protect them. They were also on ropes, and would be pulled down at the sight of enemy fighters, that way the enemy had to get close to the anti-aircraft guns to destroy the ballon. Obersvation ballons were destroyed by firing incendary bullets into the hydrogen tanks keeping it afloat. Real Zepplins were used for trans-continental flight, then bombing purposes in the Great War. That is, until bomber planes came along. A Zepplin would not be floating there during that time, seeing as there were bombers earlier on.
-AA cannon were not of the automatic type, but of a cannon type, with a single, large shell that flies up, then explodes, leaving behind a puff of smoke.