Stop App from controlling the brightness of my screen

I was on a flight watching movies on the United App. Around 8pm my screen dimmed. It dimmed a lot, to the point of being unwatchable.

Pulling the notification pane (where the brightness slider is displayed) would not let me move the brightness slider. I thought that maybe the auto-brightness was screwing with me. I went to settings, shut off the auto-brightness, and manually turned up the brightness. As soon as I re-entered the United App the brightness fell to the same level.

If I had to guess, the App turned down the brightness to keep you from disturbing other people. The problem is that the levels were too low.

How do I override the App so that I can actually see the movie? Is there a permission that I can change or another App I can use to turn the brightness back up? (Modify system setting is set to “Not Allowed”)