[quote=Rafale]
Haven't decided yet. At least in Ace Combat's structure of unlocks (from which I am taking heavy inspiration), the Tornado always comes after the A-10 (correct me if I'm wrong), which itself comes after the A-6. Again, though, haven't decided yet. I may change things around.
[/quote]

From what I can remember, the Tornado usually unlocks around the same time as the F-14, or shortly after. The Tomcat is usually in the tier of planes unlocked after the A-10, which is usually just after the F-16. 
It kind of depends on which game you're basing the aircraft 'tree' on, because it can vary quite extensively.