With the advent of the Corona virus/COVID-19, airline traffic has dropped off so much because of lack of passenger/shipper demand, and/or governmental sanitation rules, that airlines may wish to use less than 80% of their allocated slots, but then risk a loss of slots. It is a catch 22 situation: either you fly a (near) empty aircraft and keep your slot for better, post COVID times (so-called ghost flights), or you go under 80% and you lose your grandfathered slot right. Governments, other authorities and not in the least the EU, have stepped in to relax the 80/20 rule, at least temporarily. The article is divided into four parts: introduction; air transport under the Corona virus; slot allocation under Corona; slot allocation post Corona.