Im not sure what this is about but i think you offer either function for artillery against air or land. On a d6 a one in six chance is still too much… Perhaps roll 2 dice if you get a 2 then a hit is counted. Or if you got 2 artillery then a 2-3 is a hit. This attack would be preemtive. (planes are removed from play). The artillery should then be allowed to participate in normal combat with ground units. the following are some ideas for air combat missions. They are my old versions but they can help you anyway.
Air Interception of Air Units
Defending fighters may intercept and AA guns may fire at moving air units leaving the airspace of the defender’s territory or sea zone. One round of air interception combat occurs in the defender’s territory or sea zone.
Defensive Air Support
During Ground Combat Resolution, defending air units (including bombers) may move to an adjacent territory to participate in the defense of friendly ground units being attacked. Movement of these units takes one full combat round before they can be used. (Example: On round one, the defending player announces that he will dispatch fighters and on round two they are used in combat). Aircraft called up for DAS missions are not committed to fight a minimum number of combat rounds. For example: defensive Air Support was called in on combat round one and ready to fight on round two, but the defender rolled very poorly on his first round and decided to call off DAS and not risk losing his planes. At the end of ground combat resolution, surviving Defensive Air Support (DAS) units must return to their original land territory, if possible.
Combat Air Patrol
During the Non-Combat phase, you may establish Combat Air Patrol (CAP) from any territory to adjacent sea zones. Simply move any air units in range to unoccupied sea zones. Any enemy naval units (except Subs) that move into this sea zone must now stop and engage the CAP and a battle will then be fought. An enemy player can move planes to either engage the CAP, or to fly to islands in the sea zone and fight ground units or support an amphibious assault. During the regular movement phase, all CAP planes must then land on the friendly Islands or Carriers.
Coastal Defense
During Naval Combat Resolution, defending air units (including bombers) may move to an adjacent sea zone to participate in the defense of friendly naval units being attacked, or where defending naval units are conducting combat against enemy naval units that have ended their movement in the defender’s sea zone (including during amphibious assaults). Movement of these units takes one full combat round before they can be used. (Example: On round one, the defending player announces that he will dispatch fighters and on round two they are used in combat). At the end of naval combat resolution, surviving coastal defense air units must return to their original land territory, if possible.
Air units may provide coastal defense even if the land territory they are from is under attack. They may provide coastal defense, defend the land territory, or provide strategic air defense; they may not do more than one. At the end of combat resolution, if the territory a defending air unit flew from is captured, the air unit must fly to the closest friendly territory within its flight range. If no friendly territory is available, the defending air unit is eliminated.
Strategic Bombing
Bombers may perform strategic bombing against enemy ICs within their range. Strategic bombers may be intercepted by defending fighters and attacked by strategic air defense. Each bomber that survives may roll one die; this is the number of IP that the IC is reduced by during the owning country’s next turn. An IC may lose more IP than its printed value.
Fighter Escort
Fighters may accompany moving bombers or naval units as far as their range allows them and participate in air interception combat, but they may only enter two sea zones to the target territory or two sea zones and two sea zones when returning from the target territory. Escorting fighters may escort either naval units or bombers (not both) and may not attack naval units or a territory during the same turn they escort bombers or naval units.
Strategic Air Defense
Directly before strategic bombers roll for damage on an IC, defending fighters and AA guns in the territory may defend against bomber (and their escorts, if any) with one round of combat. Defending AA guns have a first-shot attack against each attacking air unit. The strategic bombers and their escorts can only target defending fighters (and not any ground units). Any surviving bombers may then bomb the IC.
