Update 3: I've established contact to noone less than the legendary id Software developer Legend John Carmack (creator of Doom, Quake, ect...) and asked him how to model such a refraction effect without raytracing. It's a honor for me to speak to him! Here's what I've learned:
Nemesis: "Hi John! Is it possible to calculate refraction of light through armored glass in real time? check:Fw190 Windscreen /youtube"
John Carmack: "Pretty easy to get quite close, but you would need ray tracing to get it exactly right with glass that isn't completely planar."
fortunately, the Fw190 Windscreen is completely planar, and shaped like a simple cuboid box!
Nemesis: "John, how to model refraction of a rectangular cuboid armor glass without raytracing? I need help on that one...any how-to?"
John Carmack: "The refraction can be baked into a projection matrix. Draw outside the window with this, clear depth, draw inside normally."
John Carmack: "Actually calculating the projection matrix will be a math chore."
Now thats good news for us flight simmers who have been waiting for more than a decade for such a great effect in real time WITHOUT large strain on the CPU/GPU. Devs? It's your turn!! Show us of what you're made of, and create the best there is on the planet for us pilots! Heck, I would even pay extra money just to have that windscreen fixed :D