(CNN) – Frontier Airlines offers free flights for people with the surname "Green" or "Greene."
The Colorado airline says it operates the "United States Greenest Flight" and is giving away flights – up to $ 400 in value – to promote Green Week, the company's eco-friendly initiative.
"Our fleet's fuel efficiency is unparalleled by other US airlines and allows Frontier to deliver not only the lowest fares but the most sustainable approach to flying," President and CEO Barry Biffle said in a statement.  The airline says that customer response has been positive.
"We are very happy to share our green message with everyone," said Zach Kramer, spokesman for Frontier Airline, adding that many people tag friends with these names. "I was surprised by how many people have the surname Green."
Passengers must book a flight at FlyFrontier.com, depart on Tuesday and return by August 20, and must legally have the surname Green or Greene.