United Airlines has apologised to a passenger after it oversold a flight and forced a two-year-old boy to sit on his mother’s lap for more than three hours.

Shirley Yamauchi and her son were on the final leg of an 18-hour journey from Hawaii to Boston when a United Airlines stewardess told her the toddler’s seat had been given to a standby passenger.

Ms Yamuachi had purchased two tickets three months in advance. She paid $1000 per ticket.

“I told him that I bought both of these tickets and he tells me that he got the ticket on standby. Then he proceeds to sit in the centre,” Ms Yamauchi told Hawaii News Now.

“What happened to my son was unsafe, uncomfortable and unfair.

“I had to move my son onto my lap. He’s 25 pounds [11.3 kilograms]. He’s half my height. I was very uncomfortable. My hand, my left arm was smashed up against the wall. I lost feeling in my legs and left arm.”

Ms Yamuachi expressed her frustrations of the incident on Facebook, calling out the United Airlines employee who reportedly shrugged off her complaints.

The man who was given her son’s seat paid just $75.

Ms Yamauchi and her two-year-old son sharing a seat. Photo: Facebook

Ms Yamuachi said was was afraid to cause a scene after she remembered recent violent incidents involving United Airlines – including when David Dao was forcibly dragged off his flight in April.

“I’m scared. I’m worried. I’m traveling with an infant. I didn’t want to get hurt. I didn’t want either of us to get hurt,” she told KITV Island News.

‘I had him in all these contorted sleeping positions. In the end, very sadly, he was standing up between my knees.”

Ms Yamuachi’s post, shared by her husband Brad Cailing. Photo: Facebook

United Airlines apologised for the incident and provided her a travel voucher as compensation.

“We deeply apologise to Ms Yamauchi and her son for this experience,” it stated.

“We are refunding her son’s ticket and providing a travel voucher. We are also working with our gate staff to prevent this from happening again.”

According to US Federal Aviation Administration (FFA) guidelines, it strongly advises against a child sitting on someone’s lap, saying, “Your arms aren’t capable of holding your child securely, especially during unexpected turbulence.”

Troubles continue for United

United Airlines has been the focus of controversy in recent months, ever since Dr Dao’s incident.

Dr Dao refused to give up his seat on an overbooked flight, and was dragged off bloodied by airport security.

Dr Dao suffered a concussion, broken nose and two missing teeth, along with other injuries.

In May, a man was detained by police after a United Airlines flight attendant reported him for placing his hand on his own son’s knee.

While in June, a United Airlines employee was captured pushing an elderly passenger to the ground.