An ability to detect mixed phase conditions and retrieve cloud properties is important for civil and military aircraft operations. This detection can help improve weather model predictions of cloud dynamics. Cloud phase is determined by the NPOESS Visible Infrared Imaging Radiometer (VIIRS) cloud mask. The VIIRS algorithm was designed to differentiate between a mixed phase condition and thin ice cloud overlapping water cloud. Different algorithms are used to retrieve properties of either water cloud or ice cloud. Hence all VIIRS cloud products depend on cloud phase determination. This paper describes the current process for detecting mixed phase clouds by the VIIRS cloud mask, some verification of the algorithm performance and strategies for improving phase detection and cloud property retrievals for future versions of the VIIRS algorithm. Comparisons of proxy MODIS satellite data with synoptic aircraft observations obtained during the Cloud Layer Experiments (CLEX) provide an initial assessment of cloud phase detection. Observations and products obtained from the CloudSat and Calipso satellite missions are considered for validating and improving the VIIRS cloud phase and cloud property algorithms.