United launched an investigation and uncovered a “brokering scheme” in which workers would ask colleagues for travel passes then sell them to outsiders.

Some employees were also found to have falsified documents so that they could name people who bought the travel passes as their relatives or domestic partners.

The airline said some workers willingly gave up their travel passes in exchange for money. Others were deceived into giving away their passes, believing that they would be given to friends or family instead.

The company fired the workers who were said to be involved in the scheme. Some believed the practice was allowed since they were not using their passes.

Frank Benenati, a spokesperson for United, clarified the company’s policy on using these special travel perks.