Six rail options for Badgerys Airport

A half-hour train trip from Sydney's CBD to the new Badgerys Creek Airport is one of six options proposed in a newly released discussion paper.

This option would, however, require a new tunnel to be built near Parramatta, a train to travel at up to 160km/h, and would be "comparatively expensive to construct", the paper says.

The federal and NSW governments released the paper on Friday and people are being urged to submit their feedback.

The simplest option for a train service to the Western Sydney Airport would be to extend the South West Rail Line from Leppington via Bringelly to the airport site using the double deck suburban trains.

"(It's) an important milestone as we plan for Western Sydney Airport, scheduled to open in the mid-2020s," Federal Urban Infrastructure Minister Paul Fletcher told reporters.

"What the PM said earlier this year is that we want to look at the question of whether rail could be operational to the ... Western Sydney Airport by the time it opens in the mid-2020s or if not then how soon afterwards,.

It follows the federal government's announcement that there will be flight path restrictions at the new airport.

The government said it would set up a community forum to give residents in the area a say in where flight paths might go.

The discussion paper can be viewed at www.westernsydneyrail.transport.nsw.gov.au.