Frontier Airlines has announced a unique promotion to celebrate their “Green Week” campaign, which highlights their efforts to become the most eco-friendly carrier in the US. As part of this week’s celebrations, anyone with the last name Green or Greene is eligible for a free domestic flight on the airline.

In order to qualify, eligible participants must depart for their one-way flights on August 13, 2019, and those booking round-trip flights must return by August 20 at 11:59pm. Participants will also have to provide official documentation of their surnames and the offer is not applicable to family members who don’t share the name.

According to Frontier, passengers who qualify will be refunded up to $400 by September 15. 

Frontier launched its “greenest flight” on Wednesday, which is from Denver, CO to Greenville, SC, on the Airbus A230neo, one of the most fuel-efficient jets in the world, according to the airline. Passengers on the flight received their refreshments in eco-friendly packaging with compostable cups and napkins, and Frontier planted trees to offset the flight’s carbon footprint.

Frontier Airlines President and CEO Barry Biffle stated in a press release that, “Our fleet’s fuel efficiency is unmatched by other U.S. airlines and allows Frontier to deliver not only the lowest fares but the most sustainable approach to flying. We are proud to serve communities across the U.S. and understand the importance of being good stewards of the environment. We’re focused on lessening Frontier’s impact on the environment and continually search for innovative solutions and technology to achieve that.”

For more details on Frontier’s “Green Week” giveaway, head to the airline’s website here.