A gas turbine bypass flow arrangement comprises an outer housing and an inner housing, an outer bypass duct defined between the outer housing and the inner housing and an inner bypass duct defined inwardly of the inner housing. A first heat exchanger is positioned at an upstream location within the outer bypass duct and a second heat exchanger is positioned within the inner bypass duct at an upstream location. A downstream heat exchanger is positioned to be in the path of air downstream of the second heat exchanger in the inner bypass duct. Air flowing across the downstream heat exchanger passes from the inner bypass duct into the outer bypass duct. A gas turbine engine is also disclosed.