The paper overviews the progress achieved by the European Commission funded project COCOMAT1 work package devoted to the development of improved simulation procedures for collapse of composite airframe structures, which take degradation into account. It has been identified by industrial applications that very accurate, but necessarily slow tools are required for the final certification, whereas reliable fast tools reducing design and analysis time by an order of magnitude, will allow for an economic design process. Twelve industrial and academic partners have been involved in the extension of commercial analysis software such as SAMCEF, B2000, ABAQUS, MSC.MARC, MSC.NASTRAN and improvement of in-house tools. In general, structural degradation has been implemented as growth of skin-stringer separation and delamination in the stiffened composite structures. Interlaminar fracture growth criteria have been implemented by means of Virtual Crack Closure Technique (VCCT) and Virtual Crack Extension (VCE) Method. Furthermore stress/strain based failure criteria such as Hashin, Puck and Maximum Stress have been introduced to model initiation and progression of the ply damage. Finally, all developed tools have been validated by means of the experimental results obtained from the other work packages within the COOCMAT1 project. Among the validation experiments were: double cantilever beam, end-notched flexure and mixed mode stiffener specimens together with stiffened panel and box structures with pre-existing and industrially pre-selected damage.