The superplastic behaviour of two aluminium alloys for aerospace applications, AA2618 and AA7075, has been investigated in high temperature tensile tests. The aim of this work has been the assessment of the values of the strain sensibility coefficient m that can be reached during the hot deformation tests by using a commercial material. Moreover, in the superplastic/isothermal forging tests the billets are maintained at high temperature for long times, so grain growth could occur limiting the potential superplasticity effect. This work deals with the assessment of the best temperature and strain range for superplastic forging of the two aluminium alloys and gives an indication of the grain growth during the high temperature heating up and soaking times. AA7075 resulted in better potential properties with respect to AA2618, but both alloys have shown a superplastic behaviour in high temperature tensile tests that could be useful for the industrial application in the isothermal forging process.