Delays at Sydney Airport after due to 'disruptive passenger'

Sydney Airport is experiencing delays after a flight from Sydney to Malaysia was turned around over NSW due to a "disruptive passenger onboard".

Malaysia Airlines flight MH122 left Sydney Airport at 1.40pm and landed safely back on the runway at 3.47pm this afternoon, where it was left sitting for nearly three hours with emergency vehicles nearby.

Video from on board the plane appears to show a man, who was wearing a backpack, threatening passengers and staff.

A flight departing from Sydney on route to Malaysia has been turned around over NSW after a mid air incident.

Malaysia Airlines said the flight was turned around due to a "disruptive passenger onboard".

"In the interest of safety, the commander of the flight made a decision to return to Sydney," a Malaysia Airlines spokesperson said.

"The flight carrying 194 passengers and five crew onboard landed safely at 3.47pm hours local time.

"The safety and comfort of our crew and passengers are of utmost importance to Malaysia Airlines."

On Monday evening, a flight tracking website showed about 60 per cent of departures were being delayed by an average of 22 minutes, and the time was increasing.

The plane is sitting on a runway surrounded by fire trucks.

A Sydney Airport spokesperson said it was supporting emergency agencies in the management of an incident at the airport.

"The airport is operational with flights arriving and departing," the spokesperson said.

"Passengers are encouraged to check directly with their airline regarding the status of their flight."

The Australian Federal Police (AFP) was called to meet the plane on arrival.

"The AFP is responding to an emergency incident at Sydney International Airport," an AFP spokesperson told 9News.

"An update will be provided at an appropriate time."