Raspberry Pi How To: Disable Wifi + Bluetooth on Pi 3

The Pi 3 comes with on-board Bluetooth and WiFi interfaces. If these interfaces are not required they can be switched off by editing the boot configuration:

sudo nano /boot/config.txt

Add the following lines to the end of the file:

# wifi off
#bluetooth off

Press Ctrl-O to save and Ctrl-X to exit the editor.
The Bluetooth interface service needs to be disabled to stop the error during boot:

sudo systemctl disable hciuart