Frontier Airlines is offering a 10% discount for a limited time. You can take advantage of this offer by booking flights between now and 11:50 PM EST on February 26th for travel anytime through June 12th, 2014. This promotion is stackable with other sale fares. Make sure you use promo code PLAYBALL when booking.
Keep in mind that Frontier is an ultra-low cost carrier comparable to Spirit and Allegiant meaning you will be charged for any little extra item including a pop or snack. However, unlike Allegiant, you will not have to pay for carry on bags as long as you book via Frontiers own website (which you will have to for this offer anyway).
There don’t appear to be any blackout dates unlike many of the promos Frontier runs which is a perk. Make sure you check out the full terms on the promo page before you book.