How to Open an Airplane Lavatory Door from the Outside.. It's simple.
Unlocking a bathroom from the outside could save a life in the right scenario. DCP is not responsible for any of the shenanigans you may cause knowing how to unlock this type of airplane bathroom. We hope you'll use this knowledge for good. Or possibly to prank your college friends.
* Step 1: Approach locked lavatory
* Step 2: Lift "LAVATORY" sign
* Step 3: Slide the knob into the unlocked position
* Step 4: Cackle because you've just unlocked the bathroom from the outside
Source: hipmunk