Summary of my proposals regarding aircraft:
There is only one round of air to air combat.
The side with the most surviving aircraft wins air superiority.
Every power gets a fighter in their capital to begin with; France gets a 2nd in Lorraine and Germany a 2nd in Munich (or a Zeppelin).
Fighters starting on the board are rated only 1* for combat. Thereafter newly purchased units go up to 2, 3 & 4 on each successive turn. Price is the same, old units remain at their original level.
Generally level equals combat rating and movement, though all planes can move 2 spaces minimum.
Since planes are likely to survive longer, consider increasing price to 8 IPC.
Planes can now conduct SBR against enemy production centres; i.e. the eight power capitals plus India & Munich.
To conduct SBR, a plane must take off from and land in the same tt. This can be contested.
My preference is for bombing to effect enemy morale, but it could be adapted to simply reduce enemy IPCs.
Enemy planes based in the target region can intercept and force air to air combat with the bomber(s) under the same rules as standard dogfights.
Thus, in the early war bombing is not feasible; but it comes into its own when level 4 machines become available.
This also emphasizes the importance of certain intermediate tts; note the position of Alsace (between Paris and Munich), Venice (2 spaces from Rome, Vienna & Munich), Poland (Berlin-Vienna-Moscow), Romania (Vienna-Constantinople-Moscow) & Mesopotamia (Constantinople-Bombay). The importance of Belgium as a base for bombing London is obvious.It could even be considered that starting units have a rating of 0, since these represent unarmed scouts. They would still count for air supremacy but without making a combat roll.