United Airlines Is Offering Taylor Swift Fans a 13% Discount on Select Flights — Here's How to Cash In 13 is famously Swift's favorite (and lucky) number.

Taylor Swift delighted fans Friday, April 19, when she released a surprise double album, "The Tortured Poets Department: The Anthology," her 11th studio album.

In celebration of the highly anticipated release — and upcoming next leg of her "Taylor Swift: The Eras" tour — United Airlines is offering a special deal for Swifties to garner the best prices for flights to her shows at the end of this summer.

The airline is offering a 13% discount on select domestic flight routes purchased Friday for travel between August 21 and November 13 of this year. In the fall, Swift brings the tour back to the U.S. for shows in Miami, New Orleans, and Indianapolis.

Related: Taylor Swift Is Making Vinyl Cool Again — and Profitable. Here's How Her Surprise Double Album Is Bringing Back the Old-School Medium.

"Let's say after exploring Cornelia Street, Louis wants to travel from New York to Miami, Florida for a long weekend," a representative for United Airlines told ABC News in an emailed statement, cheekily referencing one of Swift's songs. "By using the code 'April19' in the United app, Louis can save more than $50 on a round-trip ticket before August slips away. Of course, the total amount of the discount depends on the fare selected."

The 13% is intentional, as 13 is Swift's lucky and favorite number, and the dates selected align with the musician's next leg of tour dates in the U.S.

To cash in on the deal, United customers can log on to the app and use the code 'April19' for a chance to snag the deal.

Swift has had quite the year thanks to her "The Eras Tour" and subsequent in-theater experience, which helped boost her to billionaire status in October. She stands beside Rihanna as the only two female musicians to reach the financial feat.

Related: Taylor Swift Just Filed a Trademark That Could Mean Even More Sales

According to Pollstar, the Eras Tour is estimated to bring in anywhere from $1 to $1.4 billion by its end, with roughly seven months left to go.