The ultimate aim of the CCOntrails Spreading into Cirrus (COSIC) project is, for the first time, to build a physically based parameterization of aviation induced cirrus to determine its role in climate change. The project aims to conduct studies of water vapour, ice crystal habit, turbulence and radiative properties of contrail as it either spreads into cirrus or dissipates. Boundary conditions for LEM studies of contrail lifecycles will be delivered and Measurements of radiative forcing from spreading contrail taken for comparison to other cases. Case studies for testing later contrail cirrus parameterization in the Unified Model will be also be considered.