Passengers on a Jetstar flight from Japan to the Gold Coast were terrorised by an unruly traveller who groped a woman and viewed pornography during the trip, a man who was on the flight claims.

Twenty-nine-year-old Nathan Patterson told News Corp that the man touched his partner "in a sexual manner" during the flight.

"My girlfriend, who was sitting next to me, notified me that the gentleman (next to her) felt her twice down the right side of her body from her shoulder down past her buttocks and thigh," he said.

"I asked the passenger if he touched my girlfriend and he automatically started to apologise ... At that stage I noticed the man smelt strongly of alcohol and detected that he had about six bottles of clear liquid."

But even after Mr Patterson alerted the crew to the man's behaviour, it didn't stop.

Mr Patterson said the man started speaking Japanese aggressively to him and retrieved another bottle of vodka from the overhead locker.

After his drink was confiscated for the second time, the man got out a laptop and a pornographic magazine and began to masturbate, Mr Patterson said.

"I was very concerned and felt uncomfortable with what he was viewing and the actions he was displaying as a group of young Japanese girls were seated in the row behind and beside us."

Amazingly, staff did nothing.

The couple reported the man to AFP when the plane landed on the Gold Coast and he was charged with lewd conduct.

But Mr Patterson said that the airline's response was inadequate.

"My partner and I really felt very uncomfortable during the whole situation and feel disappointed that the staff seemed not to take the whole situation seriously," he said. "We must not have been important enough."

Jetstar told the News Corp they'd assisted police and that the man would not be flying with any Qantas Group carrier again.

"Clearly this was a distressing incident and we regret that one of our passengers was subjected to the deplorable behaviour of another passenger on-board," a Jetstar spokesperson said.