A supporter of President Joe Biden was asked to cover up a sign displaying his name by airline staff, who told her passengers found it offensive.

Jenny Grondahl was flying from Phoenix to San Diego on Southwest Airlines last week, carrying a cardboard sign that that read: “Arizonenses Con Biden.”

Designed by an artist, it was a memento of the volunteer work she’d done in Arizona before the election. She told the Washington Post the sign was important to her because “I worked very hard to register Latino voters. … And Latinos showed up, Arizona went blue.”

Ms Grondahl said she she got to the gate, a Southwest Airlines agent told her: “Many customers are offended by your sign.” She was asked to either cover it up with white paper and tape or to fold it and put it underneath her seat.

The Southwest Airlines employee also told her that if she’d been wearing a Biden t-shirt, she’d have been asked to turn it inside out.

Ms Grondahl was extremely upset by the incident and said she found herself shaking. She explained:“I’m looking around at the gate, and I’m thinking, how many of you was it — 20 out of 110 people? And how offended were you? What did you say? How could people have such a visceral reaction to seeing the name of our president on a sign?”

“It’s in Spanish” Ms Grondahl continued. “I just looked around, and I thought about humanity in general. How devastatingly horrible that someone saw a name, or a different language, on a sign that I’m carrying, and stood in line to complain to the airline staff to the point that they then had to come complain to me, and asked me not to bring this on board?”

Airlines do have control over passenger dress code and what they can bring onboard,  under the contract of carriage which passengers agree to when they buy a ticket. Enforcing or interpreting the rules can be at the discretion of airline staff.

Southwest has not commented directly on how their policy applies in this situation, but spokesman Dan Landson said in a statement:

“We pride ourselves on providing a welcoming, comfortable, and safe environment for all Customers and Employees regardless of political beliefs. We’re in conversations with the Customer to address her concerns and we hope to welcome her back on a future Southwest flight.”