The project involves the construction of a 23-kilometre (14 mi) line as part of the Sydney Metro system.

[4] Construction of the line started in December 2022 and was expected to be completed in late 2026 in time for the opening of the airport.

[9][10] In 2014, the Federal Government under then Prime Minister Tony Abbott initially had no plans to build a rail line.

[11] In 2015, then Prime Minister Malcolm Turnbull indicated that the airport would need both road and rail links to the Sydney CBD.

An extension of the South West Rail Link to the Badgerys Creek Aerotropolis was also proposed.

[18] Prior to June 2020, the only stations proposed were at St Marys, Western Sydney Airport and Aerotropolis.

[26] In June 2020, the federal and state governments announced a further $3.5 billion contribution to push the construction date earlier to late 2020.

[19] In March 2021, three consortia (Acciona, a joint venture of John Holland and Gamuda, CPB and Ghella) were shortlisted to deliver tunnelling works for the project.

A second major contract for surface and civil alignment works was awarded to CPB and United Infrastructure in March 2022.