Passengers on a Qantas flight to London that was forced to return to Perth about two hours after taking off due to a disruptive passenger, have praised the actions of the crew on board.

Qantas said the passenger was met by Australian Federal Police (AFP) officers when the aircraft landed in Perth, and taken off flight QF9.

Clare Hudson, who was travelling on the flight with her husband and three-month-old baby, witnessed the events unfolding.

Clare Hudson said the man was behaving strangely. ( ABC News: Eliza Laschon )

"He locked himself in the loo for about an hour," she said.

"Then when he came out, first of all we heard some shouting, we were about three or four rows in front of where it happened.

"Then he was squaring off against another passenger and sort of shouting in his face.

"It looked like it was going to turn into a brawl. Eventually they managed to calm him down and get him back in his seat.

"He seemed really wired and agitated.

"One of the cabin crew, one of the ladies, I think was a bit upset. But for us, luckily, we were far enough away that we didn't feel threatened.

"I think some of the passengers probably would have been quite scared."

Christine Kohli has praised the actions of Qantas staff on the flight. ( ABC News: Eliza Laschon )

Passenger Christine Kohli said cabin crew asked passengers for help to try to calm the man.

"They did ask for some assistance from some male passengers, and some passengers went and helped him. I understand he was restrained down the back of the plane."

"I think it was scary for quite a few people, one of the passengers I was with became quite agitated and quite upset, but I think the air crew were marvellous, they were very in control of the situation, they were calming passengers.

"They were very, very supportive. They got him down to the back of the plane quite quickly. It was clear he was quite an unwell man."

Passenger Robyn Guengerich said the captain was very calm.

"He said: 'We're very sorry for your interruption to your flight, the man is very unwell at the back of the plane and we've had advice that we need to turn the plane around and go back to Perth'."

"The passengers were all very accepting of that. I mean it was typical Aussie. I was proud of how all the passengers behaved."

The AFP said officers responded to a request for assistance to a flight returning to Perth Airport on Saturday evening.

It said a 32-year-old man was removed from the flight and is helping police with their enquiries.

A police officer escorts the man off the plane. ( Supplied: Clare Hudson )

The Saturday night Dreamliner non-stop flight normally takes about 17 hours.

Qantas said the extra flying time pushed the crew members over their duty limits, and the flight was rescheduled.

Passengers were provided with overnight accommodation, and eventually left Perth about 17 hours after their initial departure time.

Ms Kohli said despite the delay to her holiday, she was pleased with the actions of the crew.

"I've lost a day, but at the end of the day, Qantas have been marvellous, the fact that they made a very difficult decision to turn that plane around, and inconvenience a lot of people, I'm grateful for the professionalism and the fact that they put our safety first."

Qantas has apologised for the inconvenience to passengers, but said it takes a zero-tolerance approach to disruptive behaviour on board its aircraft.