Eight years after excavators began flattening cow paddocks for Sydney’s new $6 billion airport, four jet aircraft that were parked up outside its cargo hub on Monday signalled the ambitious project was finally “open for business”.

In marking the start of cargo flights, Western Sydney International Airport chairman Paul O’Sullivan reminded guests that “Rome wasn’t built in a day … and nor was WSI”, in a nod to the challenges that were overcome to turn a decades-long dream into a reality.

Moments after federal Transport Minister Catherine King unveiled a plaque for the new cargo precinct at Western Sydney Airport, two airport fire trucks performed a water salute to mark the historic occasion for Australia’s first major new airport in more than half a century.

One of two Qantas freighters parked up at the hub was scheduled to do the final honours at 10.25pm on Monday. In flying into the night sky bound for Brisbane, Qantas flight 7340 – operated by an A321 plane – was to become the first commercial cargo flight from the airport on Sydney’s western fringe.

Two other cargo planes – Boeing 737s operated by Texel Air and Team Global Express – departed earlier on Monday afternoon without their holds full, but their bosses made clear their aircraft would soon be back at the new airport.

The departure of QF7340 starts round-the-clock freight operations, and comes three months before passengers start filing through the curfew-free airport’s terminal in late October to catch the first domestic and international flights.

In the cargo hub’s first 24 hours, a dozen Qantas planes are scheduled to touch down and more than 160,000 parcels will pass through the airline’s new 24,000-square-metre freight facility near the southern end of the 3.7-kilometre runway.

The entire first stage of the cargo hub – also home to Menzies Aviation and Dubai-owned dnata – is capable of handling at least a quarter of a million tonnes of freight annually, ending the privately owned Kingsford Smith Airport’s monopoly in the Sydney basin.

Air cargo might be the less glamorous side of aviation but freighter aircraft flights will become a significant part of the new airport’s operations, especially in its first years.

“WSI is open for business,” airport chief executive Simon Hickey declared. “It’s a hard-fought journey – it’s been decades in the making.”

Texel Air has committed to flying Boeing 737-800 freighter aircraft to the airport, while a Saudi Arabian cargo operator has signalled its intention to follow suit.

Qantas international and freight chief executive Cam Wallace said the airline expects 96 cargo flights at the airport every week once fully operational.

“We’re very ambitious about the future here. We think there’s strong underlying travel demand as well as cargo demand,” he said.

The inaugural commercial freight flight on Monday comes two weeks after a Qantas A321 became the first cargo plane to land at the airport as part of trials. Qantas now has two dedicated A321 freighters and an A330 cargo plane based at Western Sydney Airport.

The airline’s domestic freighters will fly between the new airport and Melbourne, Cairns, Adelaide, Brisbane, the Gold Coast and Perth, carrying more than 850 tonnes of cargo a week. A schedule shows many of the freight flights will operate between late at night and the early morning.

With Qantas extending its air-freight partnership with Australia Post for another decade, the airline’s international freight flights from the airport are expected to begin early next year.

Texel Air chairman John Chisholm said a 24-hour cargo airport allowed freight to be transported when it was ready, and not when an airport’s operating window permits.

“The ability to operate without curfew restrictions creates opportunities that simply do not exist elsewhere in the Sydney market. In our business, time is often the most valuable commodity,” he said.

The 733,000-square-metre cargo precinct is big enough to handle eight large Boeing 747 freighters or 16 smaller Airbus A320 planes.

The start of cargo flights on Monday comes three months before the airport opens to passengers. Jetstar will become the first airline to fly from the airport on October 25, followed by Air New Zealand a day later.

Singapore Airlines will start flying there on November 23, while QantasLink flights are scheduled to begin on March 28 next year.

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