Sonic IR imaging has been shown great advantages as a NDE technology to detect defects such as cracks in metal/metal alloy structures. However, composites cannot simply be regarded as "black aluminum". The acoustic behavior of composites is quite different from that of metals. This study is to aim at the understanding of the effect of the structures and the relative positions of the sound source and the defect. In this paper, we present our work on developing Sonic IR imaging NDE for aircraft composite structures.