I think for Air AB, the tier 6 attackers face a unique situation, that they are completely on the mercy of the matchmaker.
9.0 is a excellent BR, and it rarely sees 10.0. That rarity is unheard of in many other BR brackets.
But don’t let it fool you; you may actually prefer uptiering, if you can somehow escape the attention of modernized Aim-9 carriers.
Downtier = get bases taken by airspawns
Uptier = get stomped by superior planes