Every time I go to the Marketplace and click on 'Airplanes' I get "ALL" but I have selected "since last visit" and "Unsold" as my choices. Why is that?
Go into the left side menu,, under "Filters" then "sold status" see which is highlighted, most likely it will be "All",, change that to "Unsold" and you should be good
I'm no computer expert, but it sounds like your computer is deleting the cookie on exit that would remember that setting, because if I change it there, it changes it in the "my settings" section also.