Nowadays aircraft inspection procedures are well-elaborated, but also expensive in many cases. The reason is that scheduled inspections are time-consuming and they seldom provide information on actual structural damage. “Structural Health Monitoring (SHM)” would be an interesting option to tailor inspection to the real needs of aircraft operations. Within the so-called “AISHA II” project, advanced solutions are being developed and a special focus is on development of solutions with a relatively high technology readiness level. The permanent sensor networks proposed are based upon ultrasonic and upon electrical and electromechanical impedance measurements. They are described in this paper, as well as a new sensor developed at the Department of Metallurgy and Materials Engineering, Leuven, Belgium, which uses the loss of percolation conductivity in a composite.