6   km / h , ▁which ▁in ▁ 1 9 3 9 ▁was ▁faster ▁than ▁that ▁of ▁the ▁main ▁Italian ▁f ighter , ▁the ▁Mac chi ▁C . 2 0 0 ▁( 5 0 4   km / h ). ▁ ▁After ▁testing ▁at ▁Gu id onia ▁it ▁was ▁proposed ▁by ▁I MA M ▁for ▁use ▁as ▁a ▁d ive ▁bom ber . ▁This ▁transformation , ▁which ▁involved ▁the ▁addition ▁of ▁d ive ▁bra kes , ▁provision ▁for ▁ 5 0 0   kg ▁bomb s ▁and ▁an ▁improved ▁forward ▁firing ▁arm ament ▁( adding ▁two ▁ 2 0   mm ▁can non ), ▁took ▁time ▁and ▁delayed ▁production . ▁The ▁resulting ▁aircraft ▁was ▁designated ▁the ▁Ro . 5 7 bis . ▁Performance ▁dropped ▁to ▁ 4 5 7   km / h ▁maximum ▁speed ▁and ▁to ▁ 3 5 0   km / h ▁at ▁cru ise ▁speed . ▁ ▁The ▁Ro . 5 7 bis ▁was ▁ordered ▁into ▁production ▁in ▁ 1 9 4 2 ▁and ▁entered ▁service ▁with ▁the ▁ 9 7 ° ▁Gru ppo ▁in ▁ 1 9 4 3 . ▁ ▁About ▁ 5 0 – 6 0 ▁aircraft ▁were ▁delivered . ▁▁ ▁It ▁is ▁said ▁that ▁the ▁Ro . 5 7 ▁could ▁have ▁been ▁the ▁long ▁range ▁inter ceptor ▁that ▁Italy ▁lack ed ▁throughout ▁the ▁war . ▁It ▁proved ▁to ▁be ▁too ▁cost ly ▁for ▁the ▁limited ▁weapons ▁it ▁carried ▁and ▁it ▁never ▁was ▁assigned ▁a ▁clear ▁role . ▁A ▁better - ar med ▁version ▁with