Frontier Airlines will discontinue service to Dayton International Airport as of May 31, Terry Slaybaugh, the airport’s director of aviation, said Friday.

Slaybaugh said that although Frontier hasn’t said as much, he believes the airline has decided not to compete with Southwest Airlines, which began service from Dayton International on Aug. 12 with a daily round-trip flight to Denver.

The flight to Denver International Airport opened connections to other Southwest destinations in the west.

Southwest connecting service promises to expand sharply in April when Southwest finishes a revamp of its reservations system in its ongoing effort to absorb the operations of AirTran Airlines, which it acquired last year.

Southwest said in 2012 that it was studying what other flights it might add from Dayton, but offered no firm timetable. Nevertheless, the airline has spent more than $1 million at the airport to expand service, Slaybaugh said, indicating more activity is in the works.

Frontier at the beginning of the year discontinued its morning flights to Denver, one of two daily flights it had from Dayton. The other is an afternoon flight to the same destination.

“They told us they have enjoyed their time in Dayton and maybe they’ll return in future,” Slaybaugh said. United Airlines also serves Denver, Slaybaugh added. “We do have a lot of service to Denver,” he added.

Slaybaugh said that in 2012 through November, Frontier had nearly 80,000 boardings in Dayton, a 6.4 percent decline from 2011. The airline started flying out of Dayton in 2005.

Frontier is initiating flights from Cincinnati/Northern Kentucky International Airport to Cancun, Mexico and the Dominican Republic this weekend, according to its website.

Frontier on Friday said it does not respond to “rumors and speculation.”