Frontier Airlines Monday announced seasonal increases in its flight frequencies between Denver International Airport and four Mexican resort destinations.

The Denver-based airline’s schedule changes take effect Dec. 19 and are on sale now.

The changes:

• Denver-Cancún — Increases from seven to 10 flights per week, with new flights on Tuesday, Saturday and Sunday.

• Denver-Cozumel — Increases from three to four flights per week, with a new flight on Sunday and additional capacity on Saturday.

• Denver-Puerto Vallarta — Increases from seven to eight flights per week, with an additional flight on Saturday.

• Denver-Los Cabos — Increases from seven to eight flights per week, with an additional flight on Saturday.

“Our customers have asked for more frequency and choice to Mexico, and we are happy to deliver it,” Daniel Shurz, Frontier VP of strategy and planning, said in a statement. “We continue to offer more flights from Denver to Mexico than any commercial carrier.”

Frontier is the second-busiest carrier at DIA after United Airlines. It is a unit of Indianapolis-based Republic Airways Holdings Inc.