A blanket of fog that reduced visibility to as little as 500 metres in parts of Sydney has lifted, but delays remain at Sydney Airport.
A number of international flights from places such as Hong Kong, Taipei and Auckland were diverted to other airports this morning.
And some flights to and from the Gold Coast and Avalon were cancelled.
A Sydney Airport spokeswoman said there were still delays of about an hour for domestic flights.
Passengers are being advised to check with their airline about the status of their flight.
Sydney Ferries services were also cancelled earlier in the morning due to poor visibility.
Transport for NSW has advised passengers that delays may still occur on the resumed services.
The fog which blanketed the greater Sydney region extended west to Bathurst, north to Newcastle and down to the Southern highlands.
Bureau of Meteorology forecaster Stephen Stefanac said it was caused by clearing rain overnight.
"Yesterday we had few showers around — yesterday evening, late last night — around Sydney. They've now cleared, the sky has cleared up as well, which has allowed the surface to cool down," he said.
"This is why we're seeing widespread fog across the greater Sydney region."
