Mr Byron said that while it would be possible for Sydney to double its passenger numbers from last year's 37 million to 74 million by 2033, that was the absolute limit.

''They [Sydney Airport] have a blueprint for growth and they say they don't need additional runways or terminals,'' he said.

''I believe what Sydney have outlined [in the draft masterplan released last week] is achievable but that at the end of the life of that plan they will be at their absolute capacity.''

Mr Byron, who has overseen a major redevelopment of Canberra Airport in recent years and has long championed better transport links, including fast rail between Sydney and the national capital, said Sydney Airport executives should be planning their post-2033 strategy now.

''What we have is a good plan to make the most of the existing asset,'' he said. ''A decision needs to be made on the next step and if it [Sydney's second airport] is not going to be Badgerys Creek then it has to be Canberra.''

Improving road and rail connections between Sydney Airport and Canberra should be an integral part of the transport redevelopments being proposed under the draft plan released on Wednesday.

Mr Byron said that experience in Europe and elsewhere showed the integration of air and high-speed rail services had a positive impact on both.

Sydney Airport's draft master plan is on public exhibition until August 30 and will go to the federal government in December.