Carley was heading home to Milwaukee after visiting her father in Atlanta with sisters Annie, 13, and Rebecca, 22, when the flap unfolded.
Rebecca said the three were led onto the jetway and told they'd have to get rid of the baby red ear slider -- named Neytiri after the princess in the movie "Avatar" -- if they wanted to reboard.
"I asked, 'What do you mean get rid of it?' and they said throw it away," she said. "I was very sad, and I felt bad for my littlest sister because it was her first pet and she was planning to take care of it herself."
While the sisters say they were told to put the animal in the trash, AirTran says they chose that themselves, despite an offer to fly later at no extra charge.
AirTran company policy bars animals other than cats, dogs and household birds in the cabin, said spokesman Christopher White. White cited a Centers for Disease Control and Prevention report that says the reptiles have been known to carry salmonella bacteria.
The sisters say they made it past security screeners and an AirTran gate agent before boarding. One flight attendant told them to stow the cage under their seat, they say.
But with the flight rolling toward its takeoff, an attendant told them the turtle wasn't allowed in the cabin.
Rebecca Helm called their father, and he began driving back to the airport. She asked an AirTran employee to make arrangements with her father to look after the pet until he could get there, but the employee refused.
"I basically had to make a really fast decision because the whole plane was being delayed," Rebecca Helm said. The bin wasn't very full and she thought the turtle could be found easily once her dad arrived, she said.
Rebecca twice declined the offer to take a later flight, White said.
"We don't have the personnel or the facilities to care for people's pets," White said.
Rebecca asked if throwing the pet away would allow for them to get back on the flight, White said. The gate agent did not tell the sisters what to do but said they could not get on the plane with the turtle, White said.
"At no time did any AirTran Airways crew member order or suggest that they put the turtle in the trash," he said.
Half an hour later, the sisters' father called, saying he wanted to come look through the trash, White said. The gate agent looked, couldn't find the turtle and assumed it had been emptied, he said.
The airline discovered Wednesday that the ramp supervisor had rescued the turtle from the trash "out of his own compassion" and given it to another crew member, who took it home for her 5-year-old son, White said.
AirTran told that crew member the original owners wanted it back, and the airline arranged for the turtle to fly as cargo to Milwaukee on Thursday, White said.
The sisters' mother reported what happened to animal rights group PETA, which sent a letter to AirTran demanding an investigation and disciplinary action.
For their part, Rebecca Helm says her sisters "are very happy to have the turtle back."