The recommendation is understood to be contained in a 20-year state infrastructure strategy being released today by Infrastructure NSW.

Buying the airport rail line and cutting ticket prices at the domestic and international stations has been estimated to cost about $300 million. The operator, Airport Link, charges an ''access fee'' on top of the CityRail fare at the four stations it operates and manages at Green Square, Mascot and the international and domestic terminals.

The former Labor government negotiated with Airport Link to reduce the fee at Green Square and Mascot to benefit local residents but did not consider doing the same at the airport stations.

A $12 access fee charged at the airport stations means a one-way adult ticket to the city costs $15.40 from the domestic and $16.20 from the international terminals.

Infrastructure NSW believes the cost of travel by rail to and from the airport is too high and improving accessibility is crucial to reducing traffic congestion.

A lobby group, the Tourism and Transport Forum, has argued the government should purchase the airport rail line. It is believed the strategy will not advocate a particular solution.

Infrastructure NSW will recommend hundreds of millions of dollars worth of upgrades to transport infrastructure around Sydney Airport.

The money should be spent on roads and public transport, including bus services to improve access from areas like South Sydney and Cronulla, the body is set to recommend.

It will also say that land in the Sydney basin such as Badgerys Creek should be protected as a possible site for a future second airport but that there is no immediate need for one to be built.

The recommendation is consistent with the state-federal report on Sydney's future aviation needs released earlier this year.

The Premier, Barry O'Farrell, yesterday reiterated his opposition to a second Sydney airport.