This paper uses the finite element alternating technique to study the effect of multiple cracks, i.e. multi-site damage (MSD), in an aluminium alloy plate. This problem arose as a result of MSD seen in the aft bulkhead of F/A-18 aircraft in service with the Royal Australian Air force (RAAF). For the particular problem under investigation, it is shown that the maximum value of the stress intensity factor can be directly estimated from a knowledge of the solution for a single crack. As a result of this investigation, it is also shown that compliance measurements may provide a useful tool for assessing the structural integrity of the bulkhead.