You cannot use Wifi in Airplane mode. Airplane mode turns off ALL radios. what you can do is to go into Settings, General, Cellular and turn off Cellular Data and Roaming. At that point, dont answer any calls and use Wifi.
It is, I just didnt have my phone in front of me. Turn on Airplane Mode, then go in and turn on Wifi. As I stated, turn off all roaming and cellular data.