When flying from St. Louis to Kerry, the time of day you decide to fly out makes little to no difference towards the overall price you’ll pay on tickets.
Lambert-St Louis (STL), located 12.7 mi from the city center, is the airport you fly out of when you book flights from St. Louis to Kerry.
These are just IATA (International Air Transport Association) codes. They are used in aviation to identify and differentiate airports. That’s why a Lambert-St Louis Airport to Milltown (Kerry) Kerry Airport flight would often be abbreviated as a STL to KIR flight.