Mesa negotiated with Aspen Airways to purchase all of their routes out of Denver except for their major ski market. Mesa would get all of the routes flown by Aspen’s Convair 580 aircraft and a no compete agreement with Aspen or any successor airline. Aspen would keep their Convairs and their BAe-146 “smurf” jets and the route from Denver to Aspen. The transition would begin on April 1, 1990, when Mesa would begin putting BE1900s on those routes. Aspen would later sell their British Aerospace jets and the Denver to Aspen route to Air Wisconsin. The Convairs were also sold off.
United Airlines wanted Mesa to get bigger airplanes for some of the markets because the loss of seating capacity by replacing 50-passenger Convairs with 19-passenger BE1900s, so Mesa started looking for a bigger airplane to fill the bill. The codeshare deal was for five years. Mesa also came up with a plan to cut back on overhead expenses by domiciling their flight crews in the outstations instead of Farmington, which would cut down on overnight hotel costs.
As mentioned before, Mesa put a few BE1300s on these routes, but only for a short time as the 1300s were replaced by BE1900s.