Wireless Signal Series: What is Airplane mode on Android phone

Airplane mode on Android phone is very useful to me (airplane mode also exists for other types of smart phones). You can go Menu -> Settings -> Wireless & Networks (for Android 2.1, Wireless controls for Android 1.6) -> Airplane mode to check/enable or uncheck/disable Airplane mode.

If you check Airplane mode, you will disable all wireless signals including mobile network signal (voice and data), wireless signal, and bluetooth (GPS signal still works). So you can not make or receive a phone call, or use 3G signal to surf Internet. Why is airplane mode useful? Intuitively, you need to check airplane mode when you are on a flight. But it is more than that. Some people put their Android phone in the bedroom at night. They need to check airplane mode before going to bed. Otherwise, they may be awaken by the phone call or incoming email notification. Airplane mode is also useful when you bring your phone to a meeting room, movie theater (Silence is Golden), church service, etc.

There is a difference about airplane mode for Android 2.1 (Nexus One uses Android 2.1) and Android 1.6 (G1 Dream uses Android 1.6). For Android 2.1, after you check airplane mode, you can still enable Wi-Fi (Menu -> Setting -> Wireless & Networks -> Wi-Fi) to surf Internet (but you can not enable bluetooth); for Android 1.6, after you check airplane mode, you can not enable Wi-Fi (can not enable bluetooth either). I do not know the change is according to the design or by accident.