§ Interim application of slot rules at Chicago O'Hare International Airport ; (a) Slot Operating Window Narrowed ; (b) Exemptions for Air Service to Small. Operated by the Chicago Department of Aviation and covering 7, acres (3, ha), O'Hare has non-stop flights to destinations in North America, South. 6 among the busiest. The Illinois Legislature cleared the way for slots at O'Hare and Midway last year, but there weren't many details about how that was going to. Dallas/Fort Worth, Denver and Chicago O'Hare took the second, third and fourth slots, respectively. HE RIGHT TO USE a runway, or to take-off and land at an airport, is called a slot. Bally's proposal for its River West casino calls for 3, slot machines and game tables, potentially leaving room for additional slots at O. . Slot machines at O'Hare and Midway could rake in nearly $37 million per year, even outpacing the terminal slots in Las Vegas. 1 "Slot means the operational author- ity to conduct one IFR landing or. Los Angeles was No. Those airports are Chicago O'Hare International Airport (ORD), Los Angeles International Airport (LAX), Newark Liberty International Airport.