Construction of Sydney's second international airport officially began today, with the Prime Minister turning the first sod on the site at Badgerys Creek.

Scott Morrison said the Coalition had achieved what other governments had only talked about.

"People talked a big game on western Sydney for years and years and years and our Government stopped talking and started doing," he said.

"This is biggest game changer I think for the city of Sydney, since the Harbour Bridge."

The Prime Minister acknowledged lingering issues such as noise and transport will still require close community consultation.

"It's a huge project, and huge projects require working through a lot of issues."

The Federal Government is investing $5.6 billion in the airport which is due to open in 2026.

It says 11,000 jobs will be created during construction and the airport will support 28,000 direct and indirect jobs five years after it opens.

Heavy machinery will move in tomorrow to begin phase one of construction — the removal of 1.8 million cubic metres of earth, to level the site.

Major earthworks are scheduled to begin next year.

New South Wales Premier Gladys Berejiklian did not attend the ceremony — the Minister for Western Sydney Stuart Ayers representing the State Government instead.

Her absence caused speculation that the Premier was too busy dealing with in-fighting over pre-selection in the blue ribbon seat of Castle Hill.