The enemy bombers that are attacking your ground troops attack in fact all troops in their patrol circle even in attack mode. This means that the attack will be spread over all ground troops and your patrolling interceptors. The enemy bombers will take damage of all the units so your ground troops and interceptors. His attack will be ineffective and he will take a lot of damage. Another good tactic fighting planes in attack mode is patrolling over the airbase he comes from so you can attack when he refuels. While refueling planes only have 25% health so they will take four times more damage then when in air.
A link to an advanced air combat guide: https://forum.callofwar.com/index.php?thread/10124-air-combat-guide-for-dealing-some-in-decent-damage/
