Lorrie Heasley of Woodland, Wash., said she plans to press a civil-rights complaint against the airline over Tuesday's action at Reno-Tahoe International Airport, halfway through Heasley's scheduled trip from Los Angeles to Portland, Ore.
"I have cousins in Iraq and other relatives going to war," Heasley told the Reno Gazette-Journal. "Here we are trying to free another country and I have to get off an airplane ... over a T-shirt. That's not freedom."
Southwest Airlines spokeswoman Marilee McInnis said several passengers complained about the shirt.
Heasley, a 32-year-old lumber saleswoman, said passengers began complaining after she and her husband, Ron, moved to the front of the cabin in Reno.
She agreed to cover the words with a sweatshirt, but when the sweatshirt slipped while she was trying to sleep, she was ordered to wear her T-shirt inside-out or leave.
She and her husband left. They arrived home in a rental car Wednesday afternoon.
McInnis said Southwest rules allow the airline to deny boarding to any passenger whose clothing is "lewd, obscene or patently offensive."
But Allen Lichtenstein, lawyer for the American Civil Liberties Union in Las Vegas, said it "might be problematic" that the airline "changed rules in the middle of a flight."
Heasley said she has been in touch with ACLU lawyers in Seattle, and wants Southwest to reimburse her for the last leg of the trip.