For holding as big an air show as the EAA AirVenture, Whitman Regional (KOSH), is not a big airport. It has just 111 aircraft based at the field, and averaged 177 air traffic control operations per day in 2015 (AirNav). Everything changes during the air show though; during the 2017 AirVenture, KOSH saw more than 10,000 aircraft arrive, and averaged 123 takeoffs and landings per hour, or a total of 17,223 operations total over the course of ten days. (EAA). According to the FAA, this places Oshkosh number 3 in the nation in terms of air traffic operations, behind Atlanta and Chicago but above Los Angeles and Dallas/Fort Worth. What’s even more impressive is that these operations took place over a ten-hour period — the other four airports are open 24 hours (FAA).
So how does this happen? Very, very carefully. A NOTAM is published with specific arrival procedures for VFR and IFR aircraft, as well as specific routes for warbirds, turbine aircraft, ultralights, helicopters, and seaplanes. The runways at Oshkosh feature large, colored circles. These, combined with an FAA waiver allowing for reduced separation of aircraft allow controllers to land multiple planes on one runway, just seconds apart from each other (EAA). To get an idea of just how this all gets accomplished, read through the real AirVenture NOTAM: