Upgraded to ios8 on my iPad air. There is no FaceTime app on the settings page to turn or or off. How to I set up face time
Since this is a strange and unusal thing that I have never heard of, I can't offer a single solution, however I can offer multiple procedures to try and solve the problem.
Turn your iPad off and back on. Simple yes, but don't underestimate the power this procedure can do. It works wonders!
If that didn't work, try resetting all of your settings. This can be acheived by opening the settings of your iPad and navigating to
General -> Reset -> Reset All Settings. This will not cause you to loose any data, however anything in the settings app will be set to their default settings, ranging from iCloud login, WiFi networks, wallpapers and even your ringtone will be set to the default. No data will be lost, but you will need to sit with the iPad for a solid few minutes reconfiguring it again to its proper settings.
Hopefully that worked, because if it didn't it's time for a device fresh restore. This is where you will need to get a computer and a USB to lightning cable and hook it up to iTunes. This procedure will force EVERYTHING to be removed from the device unless you restore it from a backup. So before you do anything, make sure you create a backup by going
File -> Devices -> Back Up. Now that you have your backup this step splits into two options for you.
a) Click on the
Restorebutton in the device summary page to wipe the device clean. Once installation is finished and while the iPad is still connected to the computer you may select
Restore From Previous Backup. This will restore everything back onto the device, including apps + their data, photos and anything else, even your wallpaper at the time. If the setting STILL isn't there. Then there is no choice to do a full restore and keep it that way
b) The best way to go about is is enable iCloud and sync all of your contacts/calendars/anything else to it if you haven't done so already. Also, a nifty new feature is iCloud Photos where it stores your photos in your drive. You can use this as a first line of backup for photos but if you want you can copy them off your computer while its still plugged in (eg iPhoto if you are on a mac). Once all your important data is backed up somewhere other than the device, hit that
Restorebutton once again. Let it finish and go through the step by step tutorial to setup as a new device.
Proceed to restore all your data by logging into iCloud/redownloading your apps/changing settings once more, but before you do any of this, check to see if the FaceTime setting is there again. If it isn't, you may as well restore from the iTunes backup once again and this time call Apple for support.
Hope it doesn't have to get anywhere further than option 1 but if all else fails I hope it works out for you. Good luck! :)