To identify hazardous (illegal and explosive) materials, microwave measurement (free space reflection type method) method has been tried to find best results in different frequency ranges. The main goal is to cluster some materials which are mainly preferred by passenger for aircraft travel. Therefore, the multivariate data analysis methods have been preferred to classify or distinguish the measured liquids. Thus, the abilities of used techniques have been shown to make the classification process easier and more responsive, while determining the convenient measurement method that can reflect the unique properties of the liquids. The desired success has been achieved magnificently by self-organizing maps algorithm.