The CAESAR project aimed to investigate the radiative properties of cirrus cloud over a wide range of wavelengths in combination with airborne in situ measurements of cirrus microphysical properties. Flights using the FAAM BAE-146 were used to observe frontal and anvil cirrus co-incident with the CloudSat Aqua-train and AATSR satellites over the Chilbolton cloud radars and lidars as well as ocean/sea surrounding the UK. Aircraft measurements were used to obtain vertical and horizontal distribution of ice crystal size, shape and IWC during summer and winter periods.