Great Lakes Airlines has issued this statement:
At midnight on Monday, 3/26/18, Great Lakes suspended scheduled flight operations as an air carrier.
Although we are ceasing flight operations, it is important to note that the company has not entered bankruptcy and will continue to operate certain segments of the business. We will continue to support the ADI flights operating between Denver, Pierre and Watertown.
Aerodynamics, Inc. continues to operate scheduled service between the cities of Denver, CO, Pierre, SD and Watertown, SD.
The previous route map in January 2014:
The new route map: