SYDNEY, Sept. 23 (Xinhua) -- With millions of Australians heading away for school holidays, an understaffed Sydney airport has seen mass flight cancellations on Thursday due to severe weather.

Severe thunderstorms saw more than 40 flight cancellations as heavy rain hit Sydney and much of the state of New South Wales (NSW), as well as parts of Queensland on Thursday.

While the Bureau of Meteorology has downgraded its severe weather warnings as of Friday morning, heavy rainfall is expected to continue in the following days.

As school holidays are set to begin on Saturday in most states around the country, and some are already on holiday since last week, Sydney's airport anticipates that almost 2.4 million passengers will pass through, with 1.65 million flying domestically and 720,000 internationally, in the period from this Monday to Oct. 9.

All of this is on top of the airport struggling to fill job vacancies left by the COVID-19 pandemic. In anticipation of this busy week, it held a second jobs fair to try to fill labor shortages.

Sydney Airport CEO Geoff Culbert said all of the organizations across the airport have been working hard to rebuild the workforce and operational performance is improving, but labor shortages are an ongoing challenge with around 4,000 open roles across the airport.

Meanwhile, the national carrier, Qantas, has scheduled larger-than-usual aircraft between the country's two largest cities, Sydney and Melbourne, as well as extra staff available in terminals, to manage the large influx of passengers to be brought by the upcoming holiday.