The current iPhone battery degradation/CPU slowdown issues, under iOS 11, ONLY affects certain older iPhone models and NOT any other iPad models.
How much free data storage space is left on your iPad Air?
Ideally your iPad Air should be maintaining 3 Gbs OR greater free data storage space.
In Settings app, General settings panel, turn OFF Background App Refresh.
In Settings app, under General settings, Reset panel, at the right bottom of the list, Reset All Settings.
In Settings app (NOT from the iOS Control Panel) turn OFF Bluetooth when not using any Bluetooth devices.
Also, in general, if you want a faster IDevice, on all of my iDevices, I turn off most of the iOS motion graphics eye candy, by simply turning ON Reduce Motion in Settings app, General, Accessibilty settings.
Make sure you aren't running scads and scads of background apps in the iOS 11 Control Panel/App Switcher.
If you are quit a good amount a background running apps.
Also, make sure you don’t have scads and scads of active website tabs running in the web browser.
Quit a good chunk of active website tabs.
A 1st gen iPad Air ONLY has 1 GB of RAM!
Try a hard reset of your iPad by holding down both the Home and sleep/wake buttons simultaneously until your iPad goes to black and restarts with Apple logo, then release the buttons.
Tap on the link below and follow all of my other iPad performance improving tips.
Slow iPad on iOS 9, 10 or 11!
Good Luck to You!