MIAMI — As Denver-based ultra-low-cost carrier Frontier Airlines adds a new daily flight between Miami International and Hartsfield–Jackson Airport, could this push Frontier’s ultra-low-cost competitor, Spirit Airlines, to finally make its own move to Miami?

Spirit currently has 48 flights out of Fort Lauderdale each day, with nonstop flights to 21 U.S. domestic and 25 international destinations, said spokesman Paul Berry.

“At Spirit we are always looking at opportunities at airports large and small, that work within our business model,” said Berry. “That said, we are happy with our operations at Ft. Lauderdale/Hollywood International as our primary gateway for South Florida, as Fort Lauderdale has a lower cost structure than Miami International, which is one important consideration for a ultra-low cost carrier like Spirit.

“While Frontier is taking steps to look more like Spirit, at this time their cost structure prevents them from being a true ultra-low cost carrier,” said Berry.

Meanwhile, Frontier spokesman Todd Lehmacher notes that the airline now has nonstop service out of Miami to Denver, Philadelphia, LaGuardia, Atlanta Washington Dulles and Chicago O’Hare, along with one-stop service to Indianapolis. The route is Frontier’s sixth out of Miami, and will start on March 6.

“You’ll slowly see Frontier move away from DOW schedules with the goal to achieve at least the regularity of daily service between cities served,” said Lehmacher. “We see an opportunity in Atlanta to stimulate the market through low fares which will allow more people to travel. The same truth holds true for Miami, that doesn’t have a low-cost, low-fare carrier serving the airport on domestic routes.”

But Mike Boyd of the Denver-based aviation consultancy Boyd Group International is confused about the carrier’s direction. “’Flying from Philly is silly’ was a Frontier bus ad in Trenton, [New Jersey] a year ago. Today, Frontier is big time silly, in Philly,” he said.

Boyd said if he could figure out what Frontier was doing, he would do two things. “The first is pack up my Ouija Board and move to ‘Vegas to play the numbers,” he said. “The second would be to e-mail Frontier and tell them – then we’d both know.”

The Frontier program is just like Spirit’s, except without CEO Ben Baldanza’s sense of humor, said Boyd. “It’s trying to generate net new super-low-fare-generated traffic in markets where flights are full into somebody else’s hub,” he said. “As long as everybody else is full, which should continue due to schedule discipline, the world will be a happy place.”

Boyd said he thinks Frontier looked at Miami’s numbers, and decided they didn’t want to mess with Spirit at out of Fort Lauderdale. “Frontier got its tush handed to them recently at Cleveland by those folks,” he said.

Frontier will have 47 weekly flights out of Miami when the Atlanta service begins. The new flight will be flown on an Airbus A319 aircraft.