Some of its flights are flown under United Express for United Airlines. They operate the Beech 1900D from Denver, Colorado's Denver International Airport to cities in the western United States for those operations.
One leg of flights not codeshared with UA are out of Minneapolis-Saint Paul International Airport in Minnesota.
They used to fly out of O'Hare International Airport to cities in the Midwestern United States, but Air Wisconsin and Atlantic Coast Airlines do that now.