I have a client whose 2 mos. old ipad air cannot connect or is incredibly slow to internet on 5Ghz wireless. No problem with 2.4Ghz SSID on same router. We really want to utilize the 5Ghz band for faster throughput and SSID congestion on the 2.4 Ghz band. Have tried most of the suggestions in this thread to no avail. Here is the interesting part: my ipad air has no problem, my android phone has no issues, Windows 8.1 ultrabook has no issues, other Apple phones have no issues, just this ipad air. All OS and drivers are up to date and are identical to my ipad air. The only difference between the ipads is that mine is set up to use 4G cellular. Given all the problems posted about 5Ghz issues and ipad airs, my best guess is that there is a batch of bad wireless network adapters in a lot of peoples new ipad airs. Mimo, channels, renaming SSIDs, resetting networks, changing routers, etc. we are all just dancing around trying to fix a hardware issue that will probably only resolved by replacing the wireless network card or the entire unit.