Back when I was renting regularly from National, ATL ran out of cars on a weekday afternoon as thunderstorms rolled through... the shuttle kept dropping more and more people off in a no-canopy Emerald Aisle lot, and we just stood there in the rain as cars emerged fitfully from the wash-and-prep area... after 30 or 45 minutes I finally drove off in a filthy GMC 12-passenger van. Never again.