A passenger on American Airlines was told her T-shirt emblazoned with "Hail Satan" was too offensive to wear on board.

On a trip from Key West, Florida, to Las Vegas, a flight attendant informed Swati Runi Goyal that she would have to change her shirt or get off the flight. Goyal was also asked if she understood what "offensive" meant. "The man said, ‘Your shirt is offensive. Do you know what that means?’" Goyal recounted. "I said, ‘I’m a foreign-born minority woman, I understand ‘offensive,’ and this shirt is not offensive.’"

The shirt, which says "Hail Satan," also features an upside-down cross and states that it was established in "666." Goyal said she was an atheist and didn't actually worship Satan and that she is a member of the Satanic Temple. "It’s an ironic shirt," she said. "People usually laugh at it, or they give me a thumbs-up because they understand the meaning behind it."

The flight attendant's request was backed up by other members of the crew, including a customer service agent. Though Goyal, 49, and her husband resisted the directive, eventually she complied with the crew members and borrowed one of her husband's shirts.

Goyal was surprised that her shirt caused offense, saying she was "wearing L.L. Bean hiking pants and vegan sneakers ... I mean, I couldn’t look like more of a nerd." American Airlines states on its website that passengers are required to wear nonoffensive clothing but doesn't detail specifically what that entails.

The airline did not initially apologize, saying, "Our flight attendants have a responsibility to all passengers in our care, and we must sometimes make difficult decisions associated with the application of our policies." Goyal later tweeted about the incident, noting a fear that the airline was practicing discrimination based on religion.

The company responded to Goyal, saying, "Discrimination has no place at American Airlines," and vowed to investigate the situation to determine what happened. "We apologize to Ms. Goyal for her experience, and we are reaching out to her to understand what occurred," it said in a statement.