In an interview with the Portland Press Herald, 61-year-old Sue Martin said she, her husband, and her guide dog had stopped over at Reagan National Airport near Washington, D.C. during a flight from Bangor, Maine to California on March 1.

When they got on the flight to California, Martin said she noticed the floor space was too small for her guide dog. But when Martin asked a flight attendant to move her to another row so that the dog could lie down, the attendant reportedly refused, and told her to leave the flight and talk to a ticketing agent.

When Martin tried to upgrade to a first-class seat with that agent, she said she was told that guide dogs cannot be in the first-class cabin. Martin said she knew that couldn’t be the case as it would qualify as illegal discrimination.

When Martin reboarded the flight, she said a passenger in the first-class cabin offered up his seat. Martin agreed, but was then approached by an American Airlines employee who said she had to get off the flight.

He told her that her “‘presence on the plane is not safe,’ or some stupid thing,” Martin told the Herald. “I’ve never been so humiliated and traumatized.”

In response to requests for comment, American Airlines said it was in contact with Martin and investigating the incident.

“We apologize to Ms. Martin for the recent experience she had on American Airlines,” a spokesperson for American Airlines said in a statement. “We take these allegations very seriously, and are thoroughly investigating. Service animals are welcome on all of our flights.”

This story has been updated to reflect comments from American Airlines.