iTunes Movies on plane

Sine you dod not mention your device I presume it to be a Mac

On your Mac or PC

Open iTunes on your Mac or PC, and select Movies or TV Shows from the menu in the upper-left corner. Click Store at the top of the window, then browse or search to find a specific title or keyword.

When you find a video that you want to buy:

1. Click the movie or TV show to go to its product page.
2. Click the Buy price. You might need to sign in with your Apple ID and password or use Touch ID.
3. Depending on what you want to do, click Watch Now or Watch Later. To download the video to your computer, click the Download button under the video's image or click .
4. To play your video, click . Or to view your videos, go to Movies > Library or TV Shows > Library.

In some countries and regions, Movies are called Films, and TV Shows are called Programmes.

Download or stream movies and TV shows from the iTunes Store ...

https://support.apple.com/en-in/HT203375

I have watched purchases iTunes movies on my iPad during flights several times. I download the movie, then go to the TV app, tap on Library and then tap on Downloaded. Once the movies are downloaded to the device, they should play without WiFi.