The peel performance of two aircraft fuel tank sealants was comprehensively investigated by means of a modified peel specimen previously developed. Experiments were carried out at five different peel angles in the range from 90 to 180 degrees using seven sealant layer thicknesses in the range from 0.1 to 5 mm. The effect of the peel rate was also investigated at a fixed peel angle and sealant layer thickness. The results were analysed in terms of the peel energy. Both peel angle and sealant layer thickness were found to affect significantly the measured peel energy of the sealants in a coupled way. In particular, it was found that the peel energy increased linearly with the sealant layer thickness, for the range considered in this study, and the rate of this increase was also found to increase as the peel angle was varied from 90 to 180 degrees. For very small sealant layer thicknesses (0.1 mm) there was no effect of the peel angle on the measured peel energy. The results were explained in terms of the amount of energy these materials dissipated upon deformation up to fracture and a relationship for the prediction of the peel energy was proposed. The peel rate was found to affect only slightly the measured peel energy, in the range studied. (C) Koninklijke Brill NV, Leiden, 2008