Thick fog has disrupted more than a dozen flights in and out of Sydney Airport.
A spokeswoman for the airport says the facility is not closed and some flights are still taking off and landing.
She says people booked on flights should contact their airline to see if they will be impacted.
A number of flights have been diverted to Brisbane and Melbourne.
Sydney Airport has warned there will be delays for most of the day as flight schedules return to normal after the fog lifts later this morning.
The Transport Management Centre says the fog is not causing problems on any major roads.
A Manly ferry was held up because of a lack of visibility, but all ferries are running.
© ABC 2012
16:53 EST The first shipment of sugar to leave the Port of Bundaberg since floods devastated south-east Queensland in January is setting sail this afternoon.