How to Disable Wi-Fi and 3G on Your Kindle Paperwhite
A recent change in the Kindle family of devices, including the Paperwhite, is that you no longer turn Wi-Fi and 3G on and off. Instead, you use Airplane mode to disable both Wi-Fi and 3G. (Smartphones use the same method and terminology, so remembering this for your phone makes it that much simpler for your Kindle.)
Aptly named, you will need this function while traveling and you are instructed to turn off your wi-fi.
To turn Airplane mode on and off, tap Menu→Settings→Airplane Mode. The button to the right is an on/off switch. When Airplane mode is enabled, a plane icon appears next to the battery charge indicator. This means you will no longer have Wi-Fi access while the plane icon is shown. When it is turned off, you see the wireless indicator (Wi-Fi or 3G).
When you are on a plane, Airplane mode must be enabled for the entire flight. You are allowed to use your Kindle Paperwhite for reading after the plane reaches an altitude of 10,000 feet and the pilot gives the okay. The Paperwhite itself must be turned off for take-off and landing and anytime the plane is flying at less than 10,000 feet.