The low-price superplastic, non-heat-treatable Al-Mg-Mn alloy 5083 has already been applied in the automotive industry, but not yet on aircrafts. Conformance with the stringent requirements for aircraft parts requires extensive R&D towards optimization of the superplastic forming (SPF) parameters and establishment of the post SPF properties. In this paper we report of an investigation carried out on SPF of 5083, in a temperature range of 480-530degreesC, at a strain rate of similar to0.001 sec(-1), to a maximum surface deformation of 100-300%, with or without applied backpressure. It was established that: Post-forming Tensile Yield and Ultimate Tensile Strength (YS and UTS) are independent of the deformation up to 300% and of void content up to 2%. Void size and volume increase rapidly at surface deformation over 100%, resulting in forming-tears due to local coalescence of voids on grain boundaries and in roughening of the "free" (non-contacting) surface. Voiding can be depressed and surface roughness improved by application of backpressure. The minimum backpressure for inhibition of voids depends on surface deformation, typically 2.5 MPa for 300%. The results of this R&D were exploited in design and manufacture of parts for new Israel Aircraft Industries produced aircrafts.