A recent flight became a woman’s worst nightmare after she says the man sitting next to her starting pleasuring himself during the trip to New Jersey.

The 25-year-old United Airlines passenger told NBC News that she felt “trapped” when her seatmate engaged in a lewd act during a roughly one-hour regional flight from Rochester, New York, over Labor Day weekend.

The woman, whose name NBC News is withholding because she is a victim of an alleged sexual offense, said she alerted flight attendants of the offense and wanted to change seats, but couldn’t because the flight was full. She was allowed to stand for part of the flight, but was required to return to her seat for landing.

However, when she and fellow passengers deplaned in Newark, the man walked off the plane “as if nothing happened,” NBC News reports. The woman said she was surprised to learn the airline did not inform law enforcement.

“I just got the sense (he) had done it before … People don’t just do those things at 6 a.m.,” she said.

The passenger also said a United gate agent told her it was her responsibility to request a police response.

United Airlines said it takes the matter seriously and has apologized to the passenger. A spokesperson said the airline is investigating the incident.

“The safety of our customers and colleagues is our top priority. We take these matters seriously and are looking into what happened,” a statement said.

The woman said she was eventually offered a $100 credit for a $400 flight.

According to the FBI, dozens of sexual assault cases are reported on commercial flights each year. The FAA and the FBI declined to comment.