Construction on a rail link to Melbourne Airport could begin within four years with the Victorian Government pledging up to $5 billion towards the long-awaited project.

The State Government said it would match the Federal Government's $5 billion commitment to get the project underway.

But travellers will still need to wait at least a decade before they board a train to get to Tullamarine.

Transport Minister Jacinta Allan said the finished rail link would still be years away.

"It's expected it would take a number of years for the actual link itself to be built," she said.

"If you look at the Metro Tunnel construction, that is taking up to six or seven years as well as other work that needs to sit around it.

"But we're wanting to see construction start by 2022 and that can happen now that we move into the full business case phase."

More than 30 million passengers used Melbourne Airport last year. ( ABC News: James Hancock )

Premier Daniel Andrews last year declared that construction on an airport rail link would be underway by the time the Metro Tunnel was finished in 2025.

But the State Government had not yet committed to matching the Federal Government's contribution to get the project started until today.

Prime Minister Malcolm Turnbull welcomed the decision by the Andrews Government to match the Commonwealth's spending.

"I'm confident that … $10 billion will enable us together to build the rail line from Melbourne to Tullamarine airport," he said.

The airport rail link is expected to cost between $8 billion and $13 billion, with the remaining costs expected to be picked up by the private sector.

An advanced business case will look at further details, including how long the train would take to get from the city to the airport and the cost of tickets.

Plans for Sunshine station expansion

Ms Allan said the preferred route for the rail line would go through Sunshine in Melbourne's west to offer regional travellers more services.

The plan would see a super station built at Sunshine which would boost services to Geelong and Ballarat.

Sunshine is the preferred route for the airport rail link, the State Government says. ( ABC News )

Ms Allan said the route required less tunnelling and was more cost effective. It would also not disturb homes or businesses in the area.

"This is really maximising and leveraging the investment that will be made in connecting the airport and this will see Sunshine become a major transport hub," she said.

"It is a logical location for this rail link to go through as it provides the wonderful connection into the regions and into the suburbs."

Earlier this month, Melbourne Airport released plans to redevelop the airport precinct, including a new domestic terminal and a major refit of international facilities.

Melbourne Airport says it expects 68 million visitors a year by 2038.

Last year more than 30 million passengers and around 250,000 tonnes of freight passed through the airport.