Your battery is designed to retain up to 80% of its original capacity at 1,000 complete charge cycles. The iPad Air’s one-year warranty includes service coverage for a defective battery. If it is out of warranty, Apple offers a battery service. If you purchased Apple care, the cost is $49 or if not and it’s out of warranty, the cost is $249.

But do try these basic steps that include:

1. Update to latest iOS
2. Check to see if there is anything going on taking over the battery. To view your usage, go to Settings > Battery. See if there are any apps consuming the battery.
3. Make sure your computer is plugged in and powered on when you’re using it to charge your iOS device via USB. If your device is connected to a computer that’s turned off or is in sleep or standby mode, your device’s battery may drain.

Here’s the link you can use to send the iPad in for repair. Beforehand, make sure you have a backup in the cloud. https://support.apple.com/ipad/repair/service

Hope this helps!