About 40 properties will be fully or partially acquired and 74 hectares of native vegetation bulldozed for construction of a $1.8 billion motorway to the new Western Sydney Airport.

Construction of the 16-kilometre M12 motorway is due to start in 2022 and be completed by 2025, about a year before the $5 billion airport at Badgerys Creek is scheduled to open.

The estimated cost of the project has already risen by more than $400 million to $1.8 billion due to an increase in land values around the site of the airport.

The M12 motorway will offer motorists a direct link to the new airport at Badgerys Creek. Credit:Peter Rae

The federal government included an extra $405 million for the motorway in the Budget in April, taking its funding to $1.45 billion. The remaining $350 million for the M12 will come from the state government.