in response to a question regarding flight physics, i whipped up a simple resource for aircraft flight physics. while its nowhere near realistic, the goal was easy, arcade style, with a splash of realism. it uses two python scripts, a startup, and a main loop.
this was created in 2.74, landscape was generated using the ANT Landscape addon, the plane was modeled by me.
Aircraft Physics Python.zip (4.78 MB)
it should work out of the box
Keys:
-W/S: Throttle (debug property [“POWER”])
-A/D: Yaw
-Up/Down Arrows: Pitch (inverted sim style)
-Left/Right: Bank
UPDATE: 11-18-2016
due to the baffling popularity of the logic brick system, i have made a logic bricks version. it should be noted that this version is far less advanced, sporting a VTOL type setup. there is a python script for the wheels, but that is not required for flight. logic bricks have been reused between states for simplicity, take caution.
Aircraft Physics Logic Bricks.zip (4.78 MB)
Keys:
-X: toggle taxi and flight
-W/S: forward/backward
-Space/C: ascend/descend
-rest are same as above
Note: in the spirit of realism, the lift force is local, so you cant fly upside down and you will slide when you bank. use the space key to counter the altitude drop and strafe. this will take some practice, but its super fun 
. lower the linear damping to 0.4 for a less controlled feel.
these setups can be used in your game with or without credit. but atleast try to learn a thing or two from them. comments or suggestions welcome.