Classic British Flight Sim

Bill (a complete Master of FS design) has done the same for "Golden Hawaii" for FS2004. You click an icon on your desktop and all the airports, AI and even auto gen scenery turn to 1930's type. Click when you are done and it goes back to now.

I thought at first you meant that the sim switched off after a certain amount of time!
The current "Mrs calypsos" has alreadt tried to vote several times