(CNN)Once again, United Airlines is dealing with a customer controversy.
Shirley Yamauchi said the airline gave away her 2-year-old son's seat on a recent flight, forcing him to sit in her lap for over three hours.
"He's 25 pounds. He's half my height," Yamauchi told CNN affiliate KHNL. "I was very uncomfortable ... I lost feeling in my legs and my left arm."
Yamauchi and the toddler were on the last leg of an 18-hour journey from Hawaii to Boston. When they stopped in Houston, a male standby passenger came on board with a ticket showing the same seat number as her son.
After a man was dragged off an overbooked United flight in April, Yamauchi said she didn't want to make a scene.
"I'm scared. I'm worried. I'm traveling with an infant," she told CNN affiliate KITV. "I didn't want to get hurt. I didn't want either of us to get hurt."
So the standby passenger sat down in the center seat. Yamauchi moved her son onto her lap in the window seat for the duration of the flight. United requires children who are 2 or older to have a purchased ticket, and the airline clearly states on its website that they must "occupy a seat."
Yamauchi told KITV she paid $969 for her son's ticket.
United said in a statement they didn't scan the toddler's boarding pass properly, which is why the seemingly empty seat was given away to another passenger. They are giving Yamauchi a travel voucher and refunding her son's ticket.
"We deeply apologize to Ms. Yamauchi and her son," the airline wrote. "We are also working with our gate staff to prevent this from happening again."
The Federal Aviation Administration says keeping a child in a parent's lap is not a safe option.
"Your arms aren't capable of holding your child securely, especially during unexpected turbulence," according to FAA guidelines.
In recent months, United Airlines also has apologized for falsely accusing a male passenger of fondling his child and been sued by another passenger who said he was shoved to the floor by a United employee in 2015.