ONT and MKE are approximately 1,709 miles apart by great-circle distance.
No. Roame's current schedule feed lists service with stops from ONT to MKE, but no nonstop service.
Airlines represented in the current schedule are Southwest Airlines (WN).
Aircraft listed in the current schedule include Boeing 737-800 Winglets (73H), Boeing 737 MAX 8 (7M8) and 7S7.