Remove the single 2.1 mm Phillips screw securing the AirPort/Bluetooth bracket to the lower case.

It is possible to remove the AirPort/Bluetooth board without removing this screw. Alternatively use the sharp end of a spudger to press the metal pressure connector (shown in orange) down through the hole in the AirPort/Bluetooth board, being careful to not break it off when prying the board up in the next step.