Cloud in-situ aircraft observations are fundamentally important for the validation of remote sensing of cloud microphysical properties and their parameterization for GCM applications. However, the analysis of in-situ aircraft data itself is a challenging task, especially for ice clouds. In the derivation of ice water content and particle mean effective size from 2D optical probes, e.g., the relations between ice particle mass and its 2D image need to be used, which introduces large uncertainties. In this study, we will discuss some issues in the analysis of ice-cloud microphysics by comparing the ice water contents derived from several widely used relations with those directly measured. We will focus on the polycrystals which are the popular shape often assumed in the GCM and remote sensing applications.