As part of a broader investigation into distress in the asphalt surface layer at a major Australian airport, significant testing was performed on cores taken from both trafficked and un-trafficked zones within two different asphalt mixes. Samples were compared for aggregate orientation, relative density, resilient modulus, wheel tracking, interface shear resistance and cyclic shear creep. There was a significant difference between the results from the trafficked and un-trafficked samples. It appeared that the changes to the asphalt caused by ‘straight-through’ aircraft trafficking increased the asphalt surface’s resistance to the severe shear forces induced by heavy braking and cornering of aircraft. It is suggested that where operationally practical, the surface should be exposed to frequent and heavy straight-through traffic for as long as possible prior to allowing harsh braking and turning operations. This would reduce the risk of early life horizontal deformations occurring in the heavy braking zones.