Traffic congestion between the city and Melbourne Airport is likely to worsen once the east-west link is built unless the Tullamarine Freeway is widened, the airport's chief warns.

The northern section of the Tullamarine Freeway already carries on average 42,000 vehicles each weekday, but has a capacity of just 40,000, according to VicRoads.

Melbourne Airport chief executive Chris Woodruff said there was an urgent need to widen the freeway north of Essendon Airport from four lanes to six to ease rising congestion.

A railway line to the airport would also take millions of cars off the road every year, Mr Woodruff said. The airport's latest five-year draft master plan, released last month, includes a new above-ground corridor for the proposed rail link, unlike the 2008 plan, where the railway entered the airport through a tunnel.