Ozark Air Lines Twin Otters

In 1972, Ozark Air Lines acquired a small fleet of Twin Otters to start high-frequency service between Springfield, Illinois and Meigs Field in Chicago.  The main appeal of this route was to connect the Illinois' state capital to its largest city.  A number of lawmakers maintain offices in both places, which evidently generates a sizeable amount of local traffic.

Air Illinois Springfield timetable dated January 17, 1972
Only 5 roundtrips were being operated, which increased to 8 by March 1

Air Illinois was already operating 8 weekday roundtrips between Springfield and Meigs, so capacity on the route more than doubled when Ozark began offering 9 weekday roundtrips on March 15, 1972.

Fold-over postcard promoting new Springfield - Chicago (Meigs) service



Interior of promotional postcard showing flight schedule



Ozark Air Lines timetable dated March 1, 1972

From the March 1, 1972 timetable
Full-page ad for Springfield - Chicago (Meigs) Twin Otter service, beginning March 15th

Perhaps Ozark thought the market would support both carriers, or that their name recognition would wrest market share away from the smaller airline, but the service lasted less than a year, with Air Illinois emerging as the victor. 

In late 1973, Air Illinois acquired a 48-seat HS 748 for use on the route.  The 748 shaved 15 minutes from the Twin Otter's flight time (about an hour), and despite a reduction in frequency to 5 roundtrips daily, capacity was significantly increased.



From the January 1, 1974 Official Airline Guide
Chicago to Springfield, IL schedules showing Air Illinois flights under codes "QX" and "UX"

 Since the carrier's commuter certificate would not permit the operation of an aircraft that large, Air Illinois operated it as an intrastate carrier, separate from its Part 135 certificate.  HS 748 flights were operated with the code "QX", as opposed to the rest of the airline's services, with flew under the more familar code "UX".  This gave Air Illinois the distinction of being one of a relatively few number of airlines to operate under 2 codes simultaneously (not including merged airlines that continued to use their predecessor's codes for some time before combining operations under a single code).