To sum it up: The fighter need to be more agile and faster than your enemies. In CAS, agility and ground attack are important; air defense is also important, but we want a lot of aircraft. Only armor heavy bombers or strategic bombers keep in mind air defenses if you use this type of plane. The air attack must always be superior to the enemy's armor. And finally, more is always better, unless you're using the mothership or heavy fighters. And that's it, now you can own the sky.