The Federal Aviation Administration (FAA) uses runway slots to limit scheduled air traffic at certain capacity constrained airports. In the U.S., those airports are John F. Kennedy International Airport (JFK), LaGuardia Airport (LGA), and Ronald Reagan Washington National Airport (DCA). In addition, the FAA monitors scheduled air traffic demand at other airports and has a formal schedule review and approval process at several airports. Those airports are Chicago O'Hare International Airport (ORD), Los Angeles International Airport (LAX), Newark Liberty International Airport (EWR), and San Francisco International Airport (SFO).
At EWR, JFK, LAX, ORD, and SFO, the FAA generally follows the International Air Transport Association (IATA) Worldwide Slot Guides (WSG) to the extent they do not conflict with U.S. laws, rules, or procedures. WSG is a set of standards and best practices developed by IATA Member airlines along with the airport coordinator and facilitator communities. These guidelines are a comprehensive set of procedures for the allocation and management of slot administration. The principal users of these guidelines are airlines, airport coordinators and airport facilitators. The Calendar of Coordination Activities specifies the deadline dates of the facilitation process to be followed by airlines and facilitators. See the current IATA Calendar of Coordination Activities (PDF). 
Carriers may contact the Slot Administration Office in the Air Traffic Organization (ATO) at the FAA for more information about operations at slot-controlled or schedule-facilitated airports: firstname.lastname@example.org.
1 The FAA publishes notice of the initial submission deadline for each scheduling season in the Federal Register. The FAA rules and orders include additional information on slot return dates and historic slot determination at U.S. Level 3 airports.