Inside the airplane you will a windshield wash liquid and disposable microfiber coath like these:
- With a water bottle or hose rinse the windshield to remove big particles.
- Spray over the windshield the wash solution and wait a few seconds.
- With the microfiber without applying much pressure to the surface, remove the wash solution (and dirt). Use all sides of the microfiber to maximize its use.
- Carefully repeat the process until the window is clean.
I recommend watching the following video for more cleaning tips: