My iPad Air has a charging problem. it says its charging but it's not!
What I would do is make sure that it is in fact the iPad that's at fault and not a power adapter, as if you use an iPhone power adapter with an iPad, it will work, but will charge it slower. NEVER use a 3rd-party charger with any Apple device, if you are, that could be the problem. If you are using the official charger that came with your iPad, it simply could be broken. So try charging your iPad with different chargers.

If your iPad is at fault, restart your iPad by holding the power button and home button together until you see an Apple logo. Try charging it again when it comes back on in a few seconds.

If that still doesn't work, make sure that your iPad Air is running the current (as of today, 11/26/15) iOS 9.1 (update: 9.2 is current now, 12/13/15). Go to Settings> General> Software Update and update it if you need to, as the charging problem could be a rare bug in an older version iOS.

If your iPad is up to date, or after you update it, if your iPad still won't charge, back it up with iTunes (see this Apple Support link, also make sure that "Encrypt Backup" is checked and set the password as your iCloud password, also be sure to back up your iPad two or three times just to be safe) and then click "Restore" (erase) your iPad in iTunes. When your iPad is restored, connect it to iTunes again and click "Restore Backup" and select the backup you made. As long as you do these steps properly, none of your data will be lost, but a clean install might just fix your charging issue.

If it still won't work after a clean install, either the dock assembly or battery is no good and will need to be replaced. If it is under warranty, call AppleCare support and see about getting your iPad fixed for free. If not, you could still go with Applecare or go with a local repair shop for a cheaper price.