The initial JetExpress partnership with Mesa ended in January 2004, when Horizon Air was selected to operate the routes. Horizon utilized slightly larger CRJ-700 regional jet aircraft on these routes. In August 2006, Frontier and Horizon planned to end their partnership. While Frontier was generally pleased with Horizon's operation, the carrier decided that it needed to revisit the agreement and find a provider with additional regional jets to grow the operation. The last of the CRJ-700s was returned to the Horizon Air fleet on November 30, 2007. As the service by Horizon Air was winding down in November, 2007, Frontier had some flights operated by ExpressJet using Embraer-145 regional jets.