- style , ▁press ur ized ▁man ned ▁flexible ▁tail gun ▁emp lacement . ▁ ▁The ▁A - 2 ▁version ▁had ▁even ▁been ▁considered ▁for ▁a ▁pione ering ▁in - fl ight ▁ref uel ing ▁cap ability , ▁possibly ▁using ▁Ju ▁ 2 9 0 ▁mar itime ▁pat rol ▁aircraft ▁as ▁the ▁tank ers . ▁With ▁in - fl ight ▁ref uel ing , ▁the ▁range ▁of ▁the ▁A - 2 ▁would ▁have ▁been ▁extend able ▁to ▁some ▁ 9 , 5 0 0   km ▁( 5 , 9 0 0   mi ) ▁of ▁total ▁flight ▁distance . ▁ ▁The ▁He inkel ▁firm ▁had ▁been ▁working ▁on ▁practical ▁co ck pit ▁press ur ization ▁methods ▁and ▁hardware ▁for ▁both ▁the ▁A - 2 , ▁and ▁slightly ▁later ▁A - 4 ▁versions ▁( ident ical ▁to ▁the ▁A - 2 , ▁except ▁for ▁the ▁fitting ▁of ▁a ▁pair ▁of ▁the ▁later ▁DB ▁ 6 1 0 ▁couple d ▁engines ) ▁from ▁ 1 9 4 0 ▁through ▁the ▁late ▁summer ▁of ▁ 1 9 4 1 , ▁when ▁the ▁DB ▁ 6 1 0 - power ed ▁A - 4 ' s ▁press ur ized ▁co ck pit ▁in ▁prov is ional ▁form , ▁almost ▁identical ▁in ▁external ▁appearance ▁to ▁the ▁standard ▁" C ab in ▁ 3 " ▁He ▁ 1 7 7 A - series ▁production ▁co ck pit , ▁was ▁ready ▁for ▁tests ▁and ▁development . ▁ ▁By ▁October ▁ 1 9 4 1 , ▁a ▁more ▁developed ▁"