Please either post a .blend or tell us more of your setup. If not it is very difficult to help you. Aircraft physics are very complicated, and depending on the level of realism you want to achieve it is necessary to use python. In other game engines I have made aircraft simulator’s.
There are five main forces that act upon a plane. Drag, Thrust, Lift, and Gravity. Then the more uncommon one is AOA. (Angle of Attack) However AOA is also involved with lift.
Drag - If you are using just a standard physics bound object, the GE does not take into account air resistance. THis is because it is usually insignificant. However at high speeds, it is so in python you would need some thing like: speed = speed * 0.95 #Gives you a decent deceleration over time.
Note that the above method would only work if you were altering it’s location directly. If you were changing the location using force, you would have to apply some negative force. (Unless there is a way to apply friction that I do not know of)
Thrust - Just alter the location directly with location, or force. Depending on wich ever one you liked better for drag.
Lift/AOA - When an aircraft is flying with it’s orientation (rotation) parallel to the ground, (Assuming the ground is flat) it is still moving up because of lift. There have been many calculation’s for lift vs. varying angles, so luckily you can use someone else’s. Link #1. Link #2.
Gravity - if you implented everything else correctly, and your airplane is to scale, you should just be able to use the GE’s default system.
Link -Roll Yaw Pitch Flight Dynamics
MAKE SURE YOU UNDERSTAND THAT
Then, You also mentioned that the airplane tends to turn like a car. An aircraft can turn one of two ways. It can change the Yaw (like a car turns) very slightly with a flap on the tailfin. The more common (And effective) way to turn though is to ROLL to the side slightly, then change the PITCH. IF you have ever ridden on an airplane you have felt the plane do this. So that would fix your turning problem.
Now for correcting the roll of the airplane. I’m assuming you mean that if the player rolled to the side, when he release the key, you want the airplane to turn upright. this is very simple actually with python.roll = roll * .98
Again, like the deceleration one play around with this to find the best value.
You can see how it is necessary to use python if you want advanced aircraft physics. IF I were coding this, I would have 6 variables. (Roll, Yaw, Pitch, Speed) Then assign these to their respictive values.
I hope that Helps!