Qantas chief executive Alan Joyce says he is open to the likelihood that a new airport at Badgerys Creek in western Sydney will be without a rail link when it opens.

"The last thing we want to do is to add cost burdens on to these things that are not justified," he said in Sydney on Tuesday.

Asked how concerned he was about an airport of the size planned for Badgerys Creek not having a rail link, Mr Joyce said it was important that such an infrastructure project was "not overdeveloped from day one" because of the relatively small number of passengers.

"You don't want to build an infrastructure facility that can carry 100 million people from day one but ... have only 2 or 3 million people using the facility and you're paying for that," he said at the CAPA Australia Pacific Summit in Sydney on Tuesday.

"It's not good for the airlines, it's not good for the taxpayer, it's not good for anybody developing it."

Mr Joyce said road and bus links would provide an adequate level of transport services for when the airport was opened in 2025 under the federal government's plans.

However, he said Sydney's second airport at Badgerys Creek would eventually need a rail link once passenger numbers rose to a level that justified it.

The federal government has said the proposed airport will open in 2025 with a single runway but without a rail connection. Under its plans, the airport will eventually be expanded to a parallel runway facility able to handle as many as 80 million passengers.

Fresh pitch

The NSW government, meanwhile, has ramped up its pitch for the federal government to help pay for a train line to the airport.

"I make no secret of the fact that the Commonwealth, through building Badgerys Creek, I think has an obligation and responsibility to the people of NSW to subsidise public transport in and around the facility that they are building," NSW Transport Minister Andrew Constance said on Tuesday.

"Yes the Commonwealth has done an incredible job investing in roads, but I'm very keen to ensure that they also invest in rail.

"If they're building an international airport, they've got to look at the linkages into the city, there is no ifs, no buts. And the key point here is that we have the opportunity to consider the extension of the metro line potentially from Bankstown to Liverpool to Badgerys Creek. Or even from the north-west metro.

Growing support

Accor Asia-Pacific chairman Michael Issenberg has joined a growing list of businesspeople from the hotel and aviation industries to call for a rail link to be built to the new airport.

"You have to have a rail connection. If you are going to build a world-class airport you have to have the overall infrastructure to go with it," he said on Tuesday.

Mr Issenberg said a rail link to a "second thriving airport hub" in Sydney would be good for business and the broader economy.

Hans Mitterlechner, an aviation consultant at Three Consulting, also said NSW risked repeating mistakes of the past if a rail line was not built to Badgerys Creek. "It is extremely short-sighted," he said of the federal government's plans for the airport to open without a line.

Their comments came a day after Paul Bredereck, the boss of regional airline Jetgo, highlighted the need for an express rail link from Badgerys Creek to Sydney CBD, given road congestion.

Peter Harbison, the executive director of aviation consultancy CAPA, has also said it would be a "farce" if the airport did not have a rail link when it opened.