Hi DylanDots,
It sounds like your iPad Air display is dimming with auto-brightness off. We're glad you've joined us in Apple Support Communities. Let's see if this helps.
There are some cases where even if True Tone is off, your iPad may dim. The most common is that the screen will dim after a time of no interaction (i.e. no multitouch or pressing buttons). When you interact with the iPad, the display should return to its previous brightness.
Additionally, as part of iOS temperature management, if the device's interior temperature exceeds the usual operating range, it may attempt to regulate its temperature to protect its internal components. You will note that the display dims or goes dark if this happens. You can check out more information in the section "Your device might get warm" in Keeping iPhone, iPad, and iPod touch within acceptable operating temperatures. This is normal and part of what your iPad does to regulate itself and its temperature.
If the issue remains, let us know what apps you're using when this happens.
We hope that helps with your question and take care!