To take advantage of the budget airline's sale, you have to buy tickets on October 23. There are some routes excluded from the sale (listed here), and the discount is only good on specific dates. Those are October 28, 30, and 31; November 1, 4, 6-8, 11, 14, 15, 29, and 30; and December 2, 4-6, 9, 12, and 13. That makes it a little messy, but it's worth slogging through for a flight this cheap.
Of course, be sure you know what you're getting into with any budget airline. There are a lot of fees such as baggage and seat reservations that could appear at any moment, like another screening of Die Hard on cable. Frontier charges for both -- baggage and seat reservations, not screenings of Die Hard -- and those fees aren't going to be reduced by the discount code. (Also, Frontier's on-time arrival rate isn't impressive.)
There are restrictions, but if you find a way to make it work, you'll have a tough time finding a cheaper flight inside the US.
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