Generally, experienced pilots become P3 on the A340 unless they are current on the B737NG or B732/3 and there is a need for FO's on the B737 fleets. Cadets and low experience PDI's generally go straight to a domestic fleet so that if they are unable to hack the conversion then SAA does not waste three years of a more deserving pilot's time on the inadequate PDI who may have otherwise been hiding their deficiencies as a P3 on the A340.