As reported by The Business Journal of Kansas City as well as The Business Journal of St. Louis:
The Spirit of St. Louis Airport (SUS) is adding another airline, St. Louis Air, to begin flights to and from Kansas City Downtown (MKC) Airport beginning on Monday June 20th.
The airline will use a six-passenger Piper PA-31 Chieftain twin-engine aircraft. Flying time is estimated at 1 hour 10 minutes. Fares are about $159 o/w.
SUS is located in Chesterfield MO, 17 miles west of St. Louis. MKC is Kansas City's Downtown Airport, which hasn't seen scheduled commercial traffic for a number of years, as far as I know. It's been in use as a GA airport for years, and all airlines relocated to MCI in the early 70s.
MKC is much closer to downtown Kansas City (right across the Missouri River from downtown) --- it'll be interesting to see if people are willing to pay that much more for service out of MKC.