All flights in and out of Sydney airport were grounded on Friday after the control tower was evacuated.

Planes circled over the airport but were unable to land after smoke was detected in the tower.

Airservices Australia tweeted that there was an evacuation in the control tower after smoke had been detected.

The Sydney Air Traffic Control Tower has been evacuated after smoke was detected. There is a full ground stop in place with no aircraft departing or arriving at this time @SydneyAirport. We will update you as soon as we know more.

— AirservicesAustralia (@AirservicesNews) March 29, 2019

Hundreds of passengers were left stranded, unable to board planes waiting to take off.

Airservices Australia later retweeted that they were not in lockdown as had been reported by the media.

Fire and Rescue NSW rushed to the area and evacuated 20 people. Nine News reported that the ‘systems issue’ that had affected the control tower was resolved at around 12pm.