“In 2018, weather systems during the three days prior to AirVenture’s opening day kept many pilots from making their final inbound flights to Oshkosh until the weather cleared on Sunday afternoon, July 22. That brought a huge wave of inbound flights to Oshkosh in a short six-hour period that afternoon. While the controllers and ground personnel did yeomen’s work to park 3,000 aircraft within a six-hour period, there are ways to do it better. Added to that, water-saturated ground areas at Oshkosh after landing made arrivals more complex, as did mass arrival groups and a large number of aircraft that had extended holds. All of those factors were considered in the draft recommendations to FAA.”
Source: Sean Elliott, EA