Dense smoke from Ontario and Minnesota wildfires has reduced visibility to under one mile at Wittman Regional Airport, jeopardizing VFR arrivals for the first major wave of aircraft at EAA AirVenture Oshkosh. The National Weather Service confirms hazardous air quality persists through noon 17 July, forcing pilots to consider IFR operations despite the FAA’s nonscheduled IFR slot reservation program effective 16 July. While NOAA forecasts visibility recovery by midday 17 July as winds shift, lingering uncertainty remains for mass arrivals scheduled 18–20 July, including 70 Mooneys, 130 Bonanzas, and 90 Cessnas. Organizers warn all mass-arrival times remain subject to weather, with potential for delays or diversions if smoke returns ahead of the 20 July opening.