Frontier use to fly to Ontario, but pulled out in October of last year and used that equipment to Little Rock. The fare battle between Ted on the route made it unprofitable and F9 did not want to continue matching prices which did not come close to covering the cost of the flight.
Occassionally a QXE CR7 painted with Frontier JetExpress will be used for Horizon flights on the coast, as well as a flight to Portland for MX from Denver.