A technique for detecting and locating structural damages is presented in this paper. It is based on the analysis of experimentally evaluated frequency response functions (FRFs) and consists of a comparison of the FRFs of the healthy structure which are assumed as reference and the FRFs collected at different times. A damage detection index interprets the differences between the FRFs. The results obtained by this technique when tested on a partial frame of a commercial aircraft were very interesting. It is possible to detect and locate all damages which were simulated/induced and also gave an indication of the extent of the damage. Moreover, the technique has the basic features required of a new NDE technique such as being non- model related and having the possibility of performing real- time monitoring.