Abstract The continued development of large high speed ships, often constructed from aluminium alloy, has raised important issues regarding the response of lightweight hull girders under primary hull girder bending. In particular, the response of lightly framed panels in compression may be influenced by overall panel buckling over several frame spaces. Therefore, to provide improved ultimate strength prediction for lightweight vessels, an extended progressive collapse methodology is proposed. The method has capabilities to predict the strength of a lightweight aluminium midship section including compartment level buckling modes. Nonlinear finite element analysis is used to validate the extended progressive collapse methodology.