Frontier Airlines flight attendants picketed at Denver International Airport Thursday after contract negotiations with the airline since September of last year reached an impasse. Among the issues at stake: sick leave and benefits.

“In 2008 we faced bankruptcy," said Adrienne Price, vice president of the Association of Flight Attendants for Frontier. "The workgroups, especially the flight attendants, took a concession so that we could save the company. And then in 2011 we took a year pay freeze, to also save the company."

The union seeks increasing pay by 30 percent over the next five years, to match the rate that flight attendants receive at Spirit Airlines.

Frontier issued a statement saying the company will continue to work with union leadership to "ensure that both they and Frontier have a successful and secure future.”