FSX Scenery--Quad Cities Int'l Airport KMLI, Illinois (IL), USA. The Quad Cities International Airport is the third-busiest airport in the state of Illinois and offers service to nearly a dozen destinations, with connections through the large legacy airline hubs. The airport also sees plenty of general aviation traffic. Modeled in this version is the airport terminal building as well as the John Deere corporate FBO terminal. By Matthew Derr.