Defensive Ability of Planes on the Ground

Trying to take down superior air forces, I had a plan. I put together a stack of 39 fighters and 16 tac. I targeted a stack of 5 fighters and 5 tac that were patrolling. When I got there, a second stack showed up. After a few minutes I had shot down 5 fighters and 5 tac. The remaining stack RTO. My fighters could not reach, so I sent the fighters and 4 tac to target a ground unit and sent the rest of the tacs to patrol over the enemy airfield. After a few minutes watching, there was only the one stack. Suddenly, another 5 similar stacks kept appearing and disappearing on the ground. After a few more minutes, I had lost 9 tacs. I think it is just stupid that aircraft on the ground can shoot down bombers. But if these stacks were there, how come I could not see them when I have a stack right over them. Then they appear. And no, they did not just land. That is another issue. Many times I have a stack approaching a stack on the ground. Just before I get there, it leaves. If I leave, it returns within minutes. Then when I approach it does this again. Is this a glitch or what?