Kids (not just infants!) can now fly for free on Frontier Airlines, but there's a catch

Parents, your next vacation could get a whole lot cheaper.

Frontier Airlines is letting kids fly for free as part of their Discount Den program.

And in a big departure from what airlines typically offer, the deal doesn't apply only to infants. Children 14 or younger can snag a free seat on select domestic flights.

So how much do all these free flights really cost? A Discount Den membership is $59.99 per year. You also have to purchase an adult seat for every free child seat.

Other things to keep in mind: The free seats are only available for select days, so planning ahead is a must. The deal also doesn't include bags, seat selections or other travel "add-ons."

However, a Discount Den membership can also get you other deals such as "exclusive access" to the airline's lowest fares and savings for up to six people on your booking.

More info on Frontier's promotion can be found on the airline's website.

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