Frontier Airlines is set to exit bankruptcy protection on Thursday as part of Republic Airways, which seems determined to run an efficient airline even if it ruffles some feathers in the process. By buying Frontier, Republic is transforming itself from a regional jet hauler of travelers for other airlines into a carrier that competes for its own passengers. Earlier this year it bought Milwaukee-based Midwest Airlines, too. Republic may move Frontier's maintenance operation out of Denver. It's grounding the last of the Boeing 717s flown by newly acquired Midwest Airlines. And it's gambling that the payoff from hauling its own customers will make up for whatever goodwill it might burn with the big-airline partners that hire it to feed passengers for them. Republic is looking at moving Frontier's aircraft maintenance and some ticketing operations out Denver because of high costs there, CEO Bryan Bedford said in an interview on Wednesday.