I think I may have found a solution. Click on the little blue arrow beside the name of your network. At the top I've seen one of two things with my iPod touch. "Auto join this network" On/Off or "Forget this Network". When my iPhone 5 wasn't automatically connecting to my home network, I saw neither. So I went back to "choose a network" and selected "other". I then manually put in all the specs for my network, Name, Security type, and password. It then of course connected me to my network. When I clicked on the blue arrow, at the top appeared "forget this network" (which wasn't previously there). Now when I enter Airplane mode, or turn off the Wi-Fi, it automatically connects when I turn it back on. Try using this manual method and let me know if it works for you!