Steven Williams dropped his mother off at Ronald Reagan National Airport. She was flying to New Jersey where she had a connecting flight to London. His 77-year old mother travels in a wheelchair and according to Williams is easily confused.

"They assist people in wheelchairs and get someone to wheel them through and basically take responsibility for that person until they arrive at their destination," said Williams.

Knowing that, he left the airport, trusting his mother in United Airlines's care. A few hours later, he received a text from a driver he hired to pick up his mother in London.

PREVIOUS: I had to pee in a cup on a United Airlines flight, mom says

"I got a text at 4:30 in the morning saying she hadn't arrived. I called the airline to make sure she was on the flight and they reassured me three or four times she was on that flight," he said.

It turns out his mother wasn't on that flight. He only found that out after hours of frantic phone calls. His mother made it to New Jersey, but Williams says United told him they bumped his mother off her connecting flight to London. He's still trying to figure out why.

"Basically she was left at the gate for 12 hours. They offered her a hotel that was miles away. She had to get there on her own steam. There's no way my mom could have pushed a wheelchair at her age, so she sat there.

PREVIOUS: Man honors dad by handing out $2 bills to every passenger on N.C. bound flight

Now Steven Williams is waiting, again, for another phone call from United.

"I want an apology and to know this won't happen again with my relatives or anyone else's relatives," said Williams.

United issued the following statement Tuesday:

"This never should have happened and we have spoken with our customer's family to apologize. We are working with our team and our wheelchair assistance vendor at Newark to review what happened and to prevent this from happening again.”

According to Williams, United called him Tuesday evening issuing that apology and offering his mother a $1,000 flight voucher.