most-dense and congested Class B airports, LaGuardia's IFR operations are governed by an FAA slot system. Operators are granted time-sensitive individual takeoff and landing rights in accordance with the International Air Transport Association's Worldwide Airport Slot Guidelines (WASG). In 2020, the FAA responded to drastic reductions in air traffic caused by the COVID-19 pandemic by suspending the expiration of unused slots at several US airports including LaGuardia. Facilities Terminals LaGuardia has three active terminals (A, B, and C) with 72 gates. The terminals are all connected by buses and walkways. Signage throughout the terminals was designed by Paul Mijksenaar. As with the other Port Authority airports, some terminals at LaGuardia are managed and maintained by airlines themselves. Terminal B was under direct Port Authority operation; however, in 2016, operation of Terminal B was transferred to a private company, LaGuardia Gateway Partners. LaGuardia is undergoing a multi-billion dollar redesign that resulted in a new Terminal B and a new Terminal C (encompassing the old Terminals C and D). Terminal A remains unchanged except for minor updates. The new layout will consist of new gate concourses as well. The new Terminal B has two gate concourses referred to as the Western Concourse (Gates 11–31) and Eastern Concourse (Gates 40–59). The new Terminal C has four gate concourses (numbered 61–69, 71–79, 82–89, and 92–98). Terminal A Terminal A, known as the Marine Air Terminal (MAT), was the airport's original terminal for overseas flights. The waterfront terminal was designed to serve the fleet of flying boats, or Clippers, of Pan American Airways, America's main international airline throughout the 1930s and 1940s. When a Clipper landed in Long Island Sound, it taxied to a dock where passengers could disembark into the terminal. During World War II, new four-engine land planes were developed, and flying boats stopped carrying scheduled passengers out of New York after 1947. The last Pan American flight left the terminal in February 1952, bound for Bermuda. Inside the terminal hangs Flight, a mural measuring in height and in length; it was the largest mural created as part of the Great Depression–era Works Progress Administration (WPA). Completed by James Brooks in 1942, Flight depicts the history of humanity's involvement with flight. The mural was painted over without explanation by the Port Authority of New York and New Jersey in the 1950s, possibly because some saw left-wing symbolism in it. After an extensive restoration