All flights out of Sydney Airport were delayed on Monday morning due to a radar failure at air traffic control with a reduced amount of arrivals and departures commecning after the outage.
Hundreds of passengers have been affected after the "technical issue" hit around 5am on Monday, on the first day of the NSW schools holidays.
"All flights at Sydney Airport are currently grounded until further notice due to an Air Traffic Control issue," a Virgin spokeswoman told AAP.
Sydney Aiport advised if people are travelling on Monday people should check with the airline for further information.
Qantas, Virgin Australia and Jetstar have confirmed the problem is affecting flights.
Virgin Australia said it would try to get all of its passengers on their way as quickly at it can after the problem is fixed.
"We will be contacting those guests who may be impacted but we encourage all guests to check the flight status page," the spokeswoman said.
