"I was terrified and disgusted throughout the flight and kept hoping that the man would stop, but he did not," said Monica Amestoy, plaintiff in the case.
At the time, Amestoy was 17 and was alone on the flight. She says she approached a flight attendant twice to report the man's actions, but that the flight attendants did nothing to help.
"The flight attendant then stated that the perpetrator's conduct was quote, 'disgusting,' but took no action to relocated Monica to another seat, or to report the offensive conduct to the flight deck," said Gloria Allred, Amestoy's attorney.
Amestoy says she was told there were no other seats available in her class.
"The attitude that the company has when someone reports an incident like this, should not be as dismissive," Amestoy said. "I think it should be taken seriously, and some way, I'm not exactly sure, of them figuring out how to make it safe for other people and other girls and young people to fly."
Amestoy's father, Tom, said he feels "betrayed" by the airline.
"I would have thought that they would have protected her instead of ignoring her pleas for help," said Tom Amestoy.
Amestoy's parents sent a letter to United, but say they received only a form letter response that did not adequately address the complaint.
Amestoy is suing United Airlines for negligence, intentional infliction of emotional distress and false imprisonment.
"None of us, who especially have daughters, would want our daughters to be in the position that Monica was in during that flight," said Allred.
United addressed the lawsuit in a statement to Eyewitness News.
"The comfort and security of our customers is our top priority, and we will closely review this complaint when we receive it," said United spokesperson Karen May.