Collaborative aircraft design is a process where the product is designed through close collaboration of designers from several disciplines usually co-dependent. A substantial part of the cost of a new product is committed in the early design phase, therefore, cost modelling should be integrated into the multidisciplinary design process to attain longer-timescale and cost-effective projects. The aviation industry needs innovative solutions, disruptive technologies to make economic growth compatible with sustainability and environmental constraints in terms of new noise rules, emission trading and increasing fuel prices. The main thesis motivation is to assess a cost estimation methodology for aircraft retrofitting at industrial level. The thesis is the result of a collaboration between University of Naples Federico II and the Leonardo Company - Aerostructure Division in the framework of the AGILE 4.0 research project.