Denver-based Frontier Airlines is celebrating a milestone at Indianapolis International Airport. The airline marked four million passengers since beginning service at the airport in 2002.

In honor of the milestone, surprised the four millionth passenger with round trip tickets.

Frontier currently serves four nonstop routes to Denver, Las Vegas, Orlando and Fort Myers, Florida.

Frontier says the airline has grown at IND by nearly 15 percent in the past year.

“We’re excited to celebrate this major accomplishment and milestone in Indianapolis,” said Zach Kramer, manager of corporate communications for Frontier Airlines in a news release. “Frontier is focused on delivering ‘Low Fares Done Right’ so people can fly and fly more often. We are incredibly appreciative of the support we’ve received from the community and our airport partner.”