She calls it discrimination, but the airline says it wasn't.
Leisha Hailey, who played Alice Pieszecki on Showtime's "The L Word," said she was just kissing her girlfriend. But according to the airline, her behavior was excessive.
A gay rights organization is getting involved to see if she was discriminated against.
"The L Word" is a show about gays and lesbians living in Los Angeles.
Hailey was traveling with her girlfriend from Baltimore to St. Louis on Monday. According to Southwest, passengers on her flight started complaining about the actress, who was kissing her girlfriend.
"I think it was because they were gay," said traveler Frank Mucifora. "Because if a man and woman kissed it wouldn't be a big deal I think, you see that all the time."
"I think it would be too much if it was a man and woman kissing too," said traveler Jocelyn Jackson. "I don't need to see all that."
When the flight landed, an attendant approached Hailey. That conversation escalated, resulting in Hailey and her girlfriend being escorted off the flight.
Traveler Cooper Hagedorn said his friend was on the flight.
"He just saw them getting escorted off, and said it was actually pretty mild mannered and quiet," said Hagedorn.
Hailey made a post about the incident on Twitter: "Since when is showing affection toward someone you love illegal? I want to know what Southwest Airlines considers a 'family.'"
Hailey says she was video and audio of the incident that have yet to be released.
Southwest Airlines issued a statement on Monday: "Our crew, responsible for the comfort of all customers on board, approached the passengers based solely on behavior and not gender. The conversation escalated to a level that was better resolved on the ground, as opposed to in flight."
Last month, Green Day lead singer Billie Joe Armstrong was kicked off a Southwest flight for not pulling up his saggy pants.
Last year, director Kevin Smith was kicked off Southwest because he was too large for a seat.
On its website, Southwest says it is the official airline for the Gay & Lesbian Alliance Against Defamation. But a senior official for GLAAD says they have to do more than release a statement to make sure all passengers feel welcome.