United Airlines has announced four new flights from Denver International Airport as the airline looks to be more competitive with regional rival Frontier Airlines.

USA Today reports that United will launch daily service to Greenville/Spartanburg, South Carolina, and Syracuse, New York, on June 6, and seasonal weekend service to Portland, Maine beginning on June 8.

Frontier Airlines already offers service on these routes.

Sunday flights also are being added to three existing destinations from Denver: Burlington, Vermont, Savannah, Georgia, and Pensacola, Florida.

Service to Fort Myers, Florida is being expanded from daily winter flights only to summer weekends.

Previously, United announced new routes from Denver to Charleston, South Carolina, Eureka, California, and Fairbanks, Alaska, commencing June 6.

United officials said tweaks to arrival and departure times in Denver will make connections easier and result in more morning flights.

Denver is United’s “fastest-growing hub, with a record of more than 500 daily departures this summer,” said Steve Jaquith, the airline’s Denver vice president.

“With the enhanced schedule, we’ll reduce the amount of time customers will spend waiting at the airport and provide better options to customers arriving on flights from smaller markets to get to destinations east and west of Denver,” he said.