As you have noticed, the left analog stick does not allow the plane to roll and loop. Only bank and climb. One flick of the right analog stick will make you roll and loop though. When you set to "Pro Flight", the right analog stick gives you free movement so that you can roll and loop in the exact way you wan to just like a real airplane. But for those who are used to doing this on the left analog stick, I suggest that you switch the analog sticks in the options menu. After this, the flying is like Ace Combat. The right analog stick will then allow you to still bank and climb... think of this as your rudders and flaps.
But in the end, I turned off Pro Flight because there's a lot of collision going on and the standard controls are more manageable.