Stephen Byron has for years pushed Canberra's case to fulfil the second Sydney airport role, in the face of entrenched resistance to a new airport at Badgerys Creek.

Mr Byron and the Canberra Business Council, backed by NSW Premier Barry O'Farrell, have put forward a high speed rail link between the national capital and Sydney as a means of saving billions of dollars in new airport infrastructure and the political fall-out from noisy planes taking off and landing over Sydney's outer west.

But more western Sydney members of parliament and business leaders are getting behind Badgerys Creek to create economic growth and quicker transport options.

Federal government announcements favouring Badgerys Creek have leaked out this year.

Infrastructure and regional development Minister Warren Truss expects a decision later this year.

A Fairfax Nielsen poll showed 72 per cent of NSW voters wanted an airport at Badgerys Creek, and quoted western Sydney MPs lobbying Mr O'Farrell to get on board.

Property commentators believe the impact on jobs and supporting infrastructure would be felt as far afield as Marulan and Goulburn on the Hume Highway, with major warehousing and logistics flourishing if Badgerys Creek operated as a 24-hour freight hub.

Canberra Airport has protected its curfew-free status vigorously, but does not see Badgerys Creek as a threat. Mr Byron said he had always supported Badgerys Creek as the best option for productivity in aviation and the economy.

''It's really the only last site. We think it is a good thing the political will is coming together. Our role is if, at some time over the next 16-25 years or so, that they move to develop, that the political will changes and they don't proceed with it, then we are the fall back position.

''The other thing we'd say is it is a long time before it will be built.''

Mr Byron is aware of a shift in sentiment in Sydney's west from anti to pro-airport.

''People have seen with the other major airports that they are important for the economy and secondly they do create a lot of jobs, so people are realising how good airports are, which is somewhat of a balance against the aircraft noise issue. Clearly aircraft have got a lot quieter over the last 30 years and what that means is people are more accepting of the benefits.''

Mr Byron said low-cost carriers such as Jetstar had made air travel more widely available, and people more supportive of flying.

He said Canberra's curfew-free status was still a key point of difference to Sydney.