Planners of Melbourne’s proposed airport rail look to have a clear choice between two routes: through Sunshine, or through Highpoint and Maribyrnong.

Trains could reach Melbourne Airport from the CBD in as little as 15 minutes, and get travellers from Geelong to Tullamarine in less than 45 minutes, even after stopping at Sunshine, according to a group of experts.

But the Maribyrnong option – understood to be favoured by the federal government, which owns a large tract of development land along the route – could link high growth-rate suburbs in the north-west into the city's rail network, offering "value capture" that could help offset the project's cost.

Value capture is a way of generating revenue from higher property values and other commercial opportunities that would spring from the route of the proposed line.