Leave in place sensor and guided wave tomographic techniques are combined together in structural health monitoring aging aircraft. In a sample problem, eight PZT transducers are mounted on the surface of the wing of an E2 aircraft. An area within a circle of 240 mm diameter is monitored with through transmission guided waves. The occurrence and progression of an artificial defect beside one rivet is clearly detected. Different computed tomography (CT) algorithms such as the back projection method, algebraic reconstruction method (ART) and multi resolution algebraic reconstruction technology (MART) are used in the defect image reconstruction with the feature of signal difference coefficient (SDC).