According to The Business Journal of Milwaukee:
Midwest Airlines has planned an event for April 13 at which time it will release details about the combination of the Oak Creek air carrier with Frontier Airlines of Denver.
Indianapolis-based Republic Airways Holdings Inc. purchased Midwest and Frontier in separate deals last year. In recent months, Republic has been evaluating how to merge the Midwest and Frontier brands.
Two weeks ago, Republic Airways' vice president of marketing and branding told The Denver Business Journal, a sister publication, that Republic will select either Frontier or Midwest as the name. No other options are under consideration.


source: The Business Journal of Milwaukee