The note can be found in the crashed plane, in the box to the right. Contains the code to the safe accessed via the keypad.
Hey buddy, I had a new safe installed aboard just in case you want to keep a few things stowed on longer flights. I set the code to 062032, my wife's birthday. Sorry to use that, but you know me - I'd forget my own name if it wasn't stitched on the front of my flight suit!