My experience is that you have to put all electronic devices off when the plan takes off and lands. Even a DAP. If you know what you're doing, you might not do this, but such rule exists to protect the innocent (read: clueless). Besides that, you must disable all radio (including WLAN, 3G, BlueTooth, ...). The rule is that you have to set the device in offline mode. Incidently, that is why that feature is called offline mode.