Frontier Airlines is celebrating Earth Day by offering an epic sale for everyone and giving away free flights to select winners. Although Earth Day is on April 22, travelers have until April 25 to get a 50% discount on their summer travel with Frontier. The promo code “FLYGREEN” will provide a cost reduction on base fares for connecting and nonstop flights through August 18. The flights can be domestic or international, but they have to be on a Tuesday or Wednesday. Also, travelers must purchase their flights at least a week before departure and book them round-trip.

Additionally, Frontier is holding an “America’s Greenest Airline Challenge,” through which randomly selected participants will win a $250 flight voucher. To win, participants must take and upload photos of themselves completing the assigned eco-friendly tasks. Entries will include submitting a designated registration form. Depending on the day, those hoping to win the free flights may have to take public transportation, show a thrifted outfit, support a local business, and more.

According to Frontier, “Users may earn bonus entries for entering on Frontier’s participating social media channels or on the landing page mentioned above, depending on which of the platforms they have already entered on for that given day.”

“From our fuel-efficient aircraft fleet to our weight-saving initiatives on board, to the stories of the animals on our plane tails, caring for the planet is central to our mission at Frontier,” said Jeff Werkheiser, Frontier Airlines’ senior director of brand and customer engagement. “In honor of Earth Week, we are thrilled to thank our customers for the steps they are taking to be green along with us by offering half-off base fares and the chance to win free flights on America’s Greenest Airline this spring and summer.”

What Else Should Travelers Know About Frontier Airlines And Earth Week?

Frontier flyers who take advantage of the Earth Day sale will still have to pay taxes and carrier fees for their airfare. You can use the discount when purchasing tickets on the carrier’s website and the mobile app. However, travelers should know that Frontier has excluded some routes from the promotion.

Adults of legal age within the U.S. may participate in America’s Greenest Airline Challenge for a chance to win. Frontier will forfeit a winner’s prize if they do not acknowledge the airline’s notification of their selection within 24 hours.