This WP is led by DTU. The end objective of the project is to come up with a detailed report of recommendations on the requirements for wind turbine lifetime extension, procedures to quantify the risk of failure and methods that establish the case for lifetime extension or decommissioning. This WP will develop the guidelines on lifetime extension based on the results of WPs 2-4, which can be a proposal for a new IEC TC88 Technical Specification (TS) on wind turbine lifetime extension as well as an input to the IEC RE. This technical specification can complement the present IEC 61400-1 standards on new wind turbine design by evaluating the reliability levels of aging structures, which is currently not within the scope of wind turbine design standards.