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 December 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.