Movies purchased in iTunes
Can I download a movie that I purchased in the iTunes Store to a thumb drive with my 5th generation iPad Air?
iPad Air 5 Wi-Fi
No. The Movie will download to the TV App on the iPad, but there's no way to get it out of there.
Also, movies form the iTunes Store will be DRM protected and even if you could get it out of the TV App, it will not play outside of authorized Apple software.