If you missed out on yesterday's promo code sale, you'll find even better fares on some Frontier routes today. Around 50 routes have dropped to just $20 each way ($39 roundtrip) for late summer/fall travel.

Availability is limited so you must be somewhat flexible to find the lowest price. Travel days will vary by route, but generally fares are available between August 13 and November 14. Pretty much all of these routes are only flown a few times each week so be sure to check out the specifics in the fare details on your route.

Tickets must be booked by 11:59 pm ET, on July 11, or before seats sell out.

Nonstop fares include:

Memphis to Orlando $34 roundtrip

Charlotte to Philadelphia $37 roundtrip

Atlanta to Miami $39 roundtrip

Pittsburgh to Orlando $39 roundtrip

Salt Lake City to Las Vegas $39 roundtrip

San Jose to Las Vegas $39 roundtrip

Atlanta to Cincinnati $39 roundtrip

Atlanta to Orlando $39 roundtrip

Cincinnati to Raleigh $39 roundtrip

Cleveland to Austin $39 roundtrip

Indiananpolis to Austin $39 roundtrip

Denver to Salt Lake City $39 roundtrip

Cincinnati to Jacksonville $39 roundtrip

Harrisburg to Raleigh $39 roundtrip

Raleigh to Providence $39 roundtrip

Jacksonville to Austin $39 roundtrip

St. Louis to Jacksonville $39 roundtrip

Birmingham to Orlando $39 roundtrip

San Antonio to Denver $39 roundtrip

Denver to Albuquerque $39 roundtrip

Detroit to Trenton $39 roundtrip

Trenton to Raleigh $39 roundtrip

New Orleans to San Antonio $39 roundtrip

Omaha to San Antonio $39 roundtrip

These fares all work in reverse as well. You'll have to decline all extras to get the lowest price.

Keep in mind that Frontier charges extra for any bags larger than a small personal item (small backpack, purse, etc.). Pack super light to get the lowest price. Checked bag fees start at $25 each way. Larger carry-on bag fees start at $30 each way.