Los Angeles was No. . Slot machines at O'Hare and Midway could rake in nearly $37 million per year, even outpacing the terminal slots in Las Vegas. Bally's proposal for its River West casino calls for 3, slot machines and game tables, potentially leaving room for additional slots at O. § Interim application of slot rules at Chicago O'Hare International Airport ; (a) Slot Operating Window Narrowed ; (b) Exemptions for Air Service to Small. 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. 1 "Slot means the operational author- ity to conduct one IFR landing or. Dallas/Fort Worth, Denver and Chicago O'Hare took the second, third and fourth slots, respectively. 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. Those airports are Chicago O'Hare International Airport (ORD), Los Angeles International Airport (LAX), Newark Liberty International Airport. HE RIGHT TO USE a runway, or to take-off and land at an airport, is called a slot.