In the matter of air to air attacks, is an airborne creature with the Pounce ability allowed to use it? Let’s look at the Pounce rules:
“When a creature with this special attack makes a charge, it can make a full attack (including rake attacks if the creature also has the rake ability).”
That’s it – so long as a creature can make a Charge attack, it can enact it’s Pounce ability, so really the Pounce is suborned under the charge rules, which are stricter (I’ve only included the salient bits):
Charging is a special full-round action that allows you to move up to twice your speed and attack during the action. Charging, however, carries tight restrictions on how you can move.
Movement During a Charge
You must move before your attack, not after. You must move at least 10 feet (2 squares) and may move up to double your speed directly toward the designated opponent.
You must have a clear path toward the opponent, and nothing can hinder your movement (such as difficult terrain or obstacles). You must move to the closest space from which you can attack the opponent. If this space is occupied or otherwise blocked, you can’t charge. If any line from your starting space to the ending space passes through a square that blocks movement, slows movement, or contains a creature (even an ally), you can’t charge.
There is nothing there that says (a) a flying creature cannot charge, or (b) the charge rules are in any way modified for creatures in the air as opposed to creatures on the ground. Charges work; therefore, Pounces are legal in air to air combat.
This creates some interesting ideas, not the least of which is that, effectively, if you have two airborne creatures fighting, each can charge on every round, since there is usually nothing in the air that would impeded the charging creature and invalidate the charge itself. In practice, the flying creature with the Pounce ability charged every round, and was able to use it’s Pounce ability every round.