iPad Air screen is black and unresponsive
I like to connect devices with no visible display to iTunes and see that I can make a backup of the device. At that point, I follow the 6 step process (even if I don't think the first few will work, sometimes going through the shutdown motions revives the screen.)


http://support.apple.com/kb/TS3281


If you can make a backup, you have a good base and then can try a restore. Also, if you haven't powered it off, that might do the trick without needing a computer.