Southwest Airlines is back with its semi-annual 72-hour sale for flights this winter. One-way fares are starting at $49 and for inter-island Hawaii travel, trips begin as low as $29.

The three-day sale covers flights in the continental U.S. between Nov. 13, 2019 and Feb. 12, 2020. If you are interested in taking advantage of Southwest's inter-island Hawaii travel, sales are valid between Dec. 4 and Dec. 18, 2019 and Jan. 2 and Feb. 12, 2019. 

International travel is also on sale for dates between Nov. 13 and Dec. 11, 2019, as well as Jan. 7 and March 5, 2020. For all the sales, there are blackout dates including most Friday and Sunday travel, largely eliminating the possibility of a quick weekend getaway. 

The winter sale ends on Oct. 3 at 11:59 PST. 

As of Tuesday morning, the cheapest fares were seen for flights either departing or arriving in to one of Southwest's hubs including Baltimore, Chicago (Midway), Tampa, Austin, Dallas (Love Field), Denver, Houston (Hobby), Phoenix, Las Vegas and Atlanta, to name a few. 

RELATED: Watch: Out-of-control catering truck nearly hits plane at O'Hare

RELATED: Safety board: Boeing should reconsider pilots' response time

The best way to find the cheapest fares is by taking advantage of Southwest's "Low Fare Calendar," which offers a calendar showing the cheapest dates to fly between two points. 

If you are unsure about your future plans but want to take advantage of the sale, Southwest also has a unique program that allows customers to cancel your ticket in return for Southwest credit that is good for a year. 

Southwest Airlines Boeing Plane
FILE - In this March 23, 2019 file photo a Southwest Airlines Boeing 737 Max aircraft lands at the Southern California Logistics Airport in the high desert town of Victorville, Calif.
AP