High-rise towers built near new train stations in Sydney's inner suburbs as part of the $20 billion-plus metro train line could pose a risk to the safety of planes flying low overhead, Sydney Airport has warned.

The advice is outlined in one of dozens of submissions made public in response to the environmental impact statement for the second stage of the new metro line from Chatswood to Sydenham via Sydney's CBD.

With construction due to intensify late next year, the City of Sydney has urged the government to build another station on the line between Waterloo and Sydenham in order to service fast-growing populations at Erskineville and St Peters.

The council is pushing for the additional station to be built under Mitchell Road or McEvoy Street in the city's inner south. It has warned that the level of demand for rail services will only increase due to residential developments in the area.