As a connoisseur of smoking regulations and unintended consequences, I love this post. Also good to know that if a captain decides, "Screw it, this is a smoking flight now," there might still be a switch for that.
United Airlines Just Grounded A Fleet Of Planes Because Its No Smoking Signs Don't Turn Off - View from the Wing
United Airlines was the first airline to create a nonsmoking section back in 1971. Delta was the first to fully ban smoking worldwide in 1994. U.S. airlines were no longer permitted to allow smoking on any flight starting in 2000. Yet planes still have ashtrays! You’ll usually find them in or near the lavatory, because customers may smoke even though it’s illegal to do so. Passengers need to be told when not to smoke. And crewmembers need to be able to turn on that sign. If they can't turn it on, because it is always on, then an exemption from the rule must be requested. Oops!
viewfromthewing.com