CHICAGO (CBS) — About two dozen demonstrators from People for the Ethical Treatment of Animals stood in front of United Airlines headquarters downtown Wednesday afternoon, holding up paper monkey masks in front of their faces.

As WBBM Newsradio’s Steve Miller reports, the protesters passed out fliers titled, “United: Stop Cruel Primate Shipments.” PETA is accusing United of giving monkeys a “one-way ticket to hell” by transporting them to research laboratories where they are killed.

LISTEN: WBBM Newsradio’s Steve Miller reports

PETA leader Tracy Patton says she does not believe medical research would suffer if monkeys were not part of the lab testing process.

“In today’s age there’s no need for this cruelty; for us to test chemicals, get animals addicted to different drugs in the name of research, when there’s more reliable ways readily available,” Patton said.

You might remember Patton from a rather dramatic protest on a day last December that was about 20 degrees colder than the temperature Wednesday. On that occasion, Patton and fellow PETA activist Crystal McCahill stripped down to bathing suits in front of a Michigan Avenue fur store.

A spokesman for United Airlines says the airline has no comment.