Severe dust storms in Sydney and along Australia’s east coast have left thousands of air passengers stranded.
Qantas said there are severe delays to both international and domestic flights.
International flights to Sydney have been diverted to Brisbane or Melbourne.
The airline is encouraging passengers with non-essential travel arrangements to reconsider their travel plans.
Jetstar said the storm was presenting "unprecedented flying conditions".
The thick red dust, blown in from the desert outback, has covered Sydney and has now reached southern Queensland.
Visibility in Sydney is so bad that harbour ferry traffic has also been disrupted.
Watch this video Sydney’s dust storm
The Opera House and other landmarks are shrouded with red dust and many residents are wearing facemasks.
The BBC said children and the elderly have been told to stay indoors and emergency services have reported a surge in calls from people with breathing problems.
Officials said air pollution levels from the dust were the highest recorded since records began in the 1970s, with 15,500 micrograms of particles per cubic metre.
By Bev Fearis
