Los Angeles was No. 6 among the busiest. Dallas/Fort Worth, Denver and Chicago O'Hare took the second, third and fourth slots, respectively. 1 "Slot means the operational author- ity to conduct one IFR landing or. § 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. 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. HE RIGHT TO USE a runway, or to take-off and land at an airport, is called a slot. 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. Those airports are Chicago O'Hare International Airport (ORD), Los Angeles International Airport (LAX), Newark Liberty International Airport. .