Monarch Airlines was an American airline based in Denver, Colorado, that began its scheduled air service on November 27, 1946 with a flight from Denver to Durango, Colorado using a Douglas DC-3. It was formed by F.W. Bonfils of The Denver Post family and Ray M. Wilson, who operated a Denver flying school. Other services started to Albuquerque, Salt Lake City and Grand Junction. Monarch had five DC3s at the merger: NC64421, NC64422, NC64423, NC64424, and NC66610. They became Frontier Sunliners Arizona, New Mexico, Royal Gorge, Mesa Verde and Utah.