Go faster and slower and he will get used to it. My horse Parfae always bucked reared was super spooky By one spot in my arena and I’ve been getting him used to i
Walk them over there, back them up, and repeat,
I would just walk over by them a lot, and once hes used to them at a walk, go to a trot, etc.. Mostly just keep his mind off of it, make him walk/Trot/canter faster, slower, stop, back up, etc while going towards the window. This helps me when my horse spooks. Good luck!
Maybe put some mirrors near his paddock (like in an adjacent paddock) and put some in your arena, he might be spooking at his reflection or the light? Otherwise Park your car near where you're working him and ride around your car (or float) so he get some used to the reflection of lift off windows?
Do an exersize near the windows, that way his focus is on you and he should be less spooky when going near the windows
Just let him get used tho them by standing by them. Or leg yields near them. And ALOT of encouragement and pats