Fiber reinforced composite plate-like structures have been used to achieve substantial reductions in the structural weight of both military and commercial aircrafts. For large area and layered structures, damage detection using any conventional testing methods is time consuming. Structural Health Monitoring (SHM) of such structures is seen as a new paradigm that will reduce maintenance costs and increase safety. The aim of the technology is to provide an early indication of physical damage. The early warning provided by an SHM system can then be used to define remedial strategies before the structural damage leads to failure. This paper describes the development and successful demonstration of a SHM system using Smart Flexible Sensor Patch (FSP) that has a built-in network of Piezoelectric Wafer Active Sensors (PWAS) embedded on a thin film of dielectric material. These PWAS are arranged such that conventional cross-hole tomography (CHT) as well as modified cross-hole tomography (MCHT) can be carried out using Lamb waves. Using MCHT, the lateral extent of the damage for barely visible low-velocity impact damages (BVID) on Composite structures like wing and aileron are were imaged. The conventional CHT was deployed in a region of large aspect-ratio such as stiffeners. It was observed that disbonds of stiffener in Eleven and other structures may be effectively monitored by this method. © 2007 American Institute of Physics.