International aircraft will begin to use Sydney Airport's existing domestic terminals and car parking and roads links bolstered under long-term expansion plans to cope with surging passenger demand.

A 20-year blueprint for Australia's busiest airport – released on Monday – also shows the operator believes the “optimal route” for a motorway link to the WestConnex tollroad will be through a 13-hectare block of land north of Kingsford Smith.

Sydney Airport has plans for some international flights to arrive and depart at the existing domestic terminals. Credit:David Moir

The “northern lands” are held by the airport under a 99-year lease, and have complicated the Berejiklian government's plans for a $1.8 billion road link known as the Sydney Gateway between an interchange for WestConnex at St Peters and the airport and Port Botany.

Sydney Airport wants to develop the northern lands to include new freight facilities, and support services for catering, and vehicle storage.