Monitoring structural health of civil and industrial structures, based on in-operation modal testing, has become an important issue. Recently, a sensitivity-based damage assessment technique was presented and successfully tested on both civil and more academic structures. As shown in literature, these sensitivities can be experimentally calculated (without the use of a finite element model) on a basis of the estimated natural frequencies and mass-normalised mode shapes of the test structure in its reference condition. Since a driving point measurement is required for an easy scaling (e.g. mass-normalisation) of the mode shapes, the applicability of the method was restricted to forced-vibration tests only. In this contribution, the applicability of the sensitivity-based method is extended to the domain of operational modal analysis (output-only measurements). In a first step, a new method is used for the correct re-scaling of operational mode shape estimates that neither requires forced vibration testing nor finite element modelling. Secondly, two innovative sensitivity-based in-operation damage assessment schemes are introduced. Both methods were experimentally tested on an academic frame structure as well as a slat track of an Airbus A320 commercial aeroplane.