Fairfax Media business manager Katrine Norlyng was woken by the shouts of police officers as they sat the handcuffed passenger down in the seat in front of her.

"He was intoxicated in some way. I wouldn't say he was drunk but he would've been under the influence of something," she said.

"I woke up and there was this commotion and police yelling at him to shut up and calm down."

The 36-year-old man from Kiama, on the south coast, was arrested by Australian Federal Police officers who were on the Qantas flight on Friday night.

He was dressed "pretty casual" and had been seated in economy before police brought him into business class to sit with them.

"There were a couple of incidents where he did seem to be confused about what was going on," Ms Norlyng said. "He was questioning why there were police on the plane.

"After a while he calmed down and they gave him Coke and sandwiches."

Fairfax Media is the publisher of this website.

Police say they charged the man after he allegedly punched a fellow passenger in the face repeatedly as the passenger tried to sleep.

The AFP said the man did not know his alleged victim before he punched him.

On the third strike, the passenger tried to block the punch and yelled to the crew for help, the AFP said, and officers who were on the flight detained the man until the plane landed in Sydney.

The alleged victim suffered cuts and bruises to his face and received medical treatment from a doctor who was on the flight.

The man was charged with assault occasioning actual bodily harm and obstructing a territory official.

"The AFP will not tolerate this type of behaviour. Aviation safety is a serious matter and abusive behaviour poses a serious risk to the travelling public," AFP aviation manager Michael Chew said.

"Those who behave violently on board aircrafts can expect to be charged."

The Kiama man was granted bail to appear in the Downing Centre Local Court on September 30.