Air New Zealand flights bound for Sydney were forced to turn back to New Zealand on Wednesday due to dust storms and high winds in New South Wales.
Clouds of red dust whipped up by storms in the outback blanketed Sydney and large parts of New South Wales in the morning, before spreading to Brisbane and the southern part of Queensland.
The storm affected about 1500 travellers to and from New Zealand across three airlines.
Air New Zealand says a larger 747 plane carrying about 400 passengers helped to clear the backlog of waiting travellers on Wednesay afternoon.
Three flights returned to New Zealand in the morning, as they were unable to land due to poor visibility. The three return flights from Sydney were cancelled.
The dust storm also delayed an afternoon service from Christchurch. Pacific Blue says about 300 passengers were affected.
Jetstar says all its passengers have been able to reach their destination, but with delays of up to three hours.
Qantas flights from New Zealand to Sydney were diverted to Melbourne or Brisbane.
Sydney resident Josie Nagel, who returned to Wellington on Wednesday afternoon, told Radio New Zealand she spent a frustrating day watching her flight being cancelled and uncancelled three times.
Ms Nagel said when her flight left she was scared it would not get off the ground and the clouds beneath the plane remained red until half-way across Tasman Sea.
Meanwhile, flights were cancelled and delayed in Sydney and Brisbane as the dust storm moved to Queensland, the ABC reports. Passengers at Sydney airport were facing delays of up to six hours for international flights and 90 minutes for domestic trips.
Damaging winds are forecast for Sydney, where ferry services were cancelled on Wednesday morning.
Australia's Bureau of Meteorology said the dust storm is the worst to hit New South Wales in almost 70 years.
It said the severity of the dust cloud would ebb and flow during the day as strong winds continued to batter the state, but the dust is not expected to abate until winds weaken on Wednesday night, the ABC reports.
The dust shrouded Sydney in a red glow on Wednesday. People with asthma or breathing difficulties were urged to keep their windows shut and to stay indoors.
In Victoria, a flash flooding warning has been issued, while a fire weather warning has been issued for southern parts of Queensland and northern parts of New South Wales.
Meanwhile, two small earthquakes struck Melbourne's south-east on Tuesday night. There were no reports of damage.
On Tuesday, gale force winds whipped up heavy dust storms and powerful electrical storms across parts of New South Wales.