The hate when people say to keep it in airplane mode. You do realize airplane mode also disables Bluetooth, which means no wireless controllers. So airplane mode will only work if you intend on only using handheld mode or plan on always using a wire. Best method is to just turn off wifi, or set up a fiddler proxy if you still want to use web browser
You do realize that flight mode lets you turn on and off each component as you wish, controller connection (bluetooth), WI-FI, and NFC?