If you have your computer on an airplane (or some other area where wireless connections are not allowed), you should switch off your wireless. You may also want to switch off your wireless for other reasons (to save battery power, for example).
Using Airplane Mode will completely turn off all wireless connections, including Wi-Fi, 3G and Bluetooth connections.
To turn on airplane mode:
Open the Activities overview and start typing Wi-Fi.
Click on Wi-Fi to open the panel.
Switch the Airplane Mode switch to on. This will turn off your wireless connection until you disable airplane mode again.