Many years ago I was flying from my home airport of Pittsburgh to Houston, Texas on board an ExpressJet Embraer 145.  I had a bit too much coffee and water while waiting for the flight, and figured I would use the lavatory once we were airborne.  Upon reaching our cruising altitude, I made my way to the sole lavatory in the back of the plane.  I had been watching and waiting for the moment we could move around, and didn’t understand how it was occupied.

A nearby passenger told me it was no operational, and my heart fell.  I thought, “there is no way we could fly a 3+ hour flight with no working toilet”.  Then a moment later, an off duty airline mechanic told me, “let me show you a little secret on how to open it”.  This is what he taught me.

Every airplane lavatory has a little sign or placard on the door that says “Lavatory”.  That sign isn’t just there to inform people what is behind the door.  It is actually a secret compartment.  If you lift up the metal piece, there will be a little sliding mechanism beneath it.  Simply slide the mechanism and the door will suddenly unlock.  I hope this helps someone on their future travels!