▁President ▁Ro ose vel t ▁and ▁the ▁Go ody ear ▁t anks ▁were ▁subsequently ▁placed ▁in ▁service ▁in ▁Go ody ear - produ ced ▁C ors air ▁f igh ters , ▁as ▁well ▁as ▁other ▁aircraft . ▁By ▁ 1 9 4 2 ▁Fire proof ▁T anks ▁had ▁developed ▁the ▁first ▁flexible ▁fuel ▁bl add ers ▁as ▁range ▁ext ender ▁t anks ▁for ▁the ▁M k ▁IX ▁Sp it fire . ▁These ▁t anks ▁were ▁flexible ▁containers , ▁made ▁of ▁a ▁l amin ated ▁self - se aling ▁material ▁like ▁vul can ized ▁rub ber ▁and ▁with ▁as ▁few ▁se ams ▁as ▁possible ▁to ▁minim ize ▁leak ▁paths . ▁ ▁As ▁early ▁tests ▁showed ▁that ▁impact ▁could ▁over press ur ize ▁a ▁fuel ▁tank , ▁the ▁self - se aling ▁fuel ▁cell ▁is ▁susp ended , ▁allowing ▁it ▁to ▁abs orb ▁shock s ▁without ▁ru pt ure . ▁U . S . ▁Navy ▁fuel ▁t anks ▁during ▁the ▁war ▁were ▁able ▁to ▁with stand ▁ ▁bul lets ▁and , ▁on ▁occasion , ▁ ▁can non ▁shell s . ▁ ▁Not ▁all ▁f igh ters ▁were ▁fitted ▁with ▁the ▁relatively ▁new ▁in vention . ▁Self - se aling ▁t anks ▁t ended ▁to ▁be ▁heav ier ▁with ▁lower ▁capacity ▁than ▁non - se aled ▁t anks . ▁Non eth eless , ▁aircraft ▁that ▁were ▁fitted ▁with ▁self - se aling ▁t anks ▁regularly ▁took ▁more ▁pun ishment ▁than ▁those ▁without , ▁and ▁were ▁able ▁to ▁return ▁to ▁base . ▁Com bat ▁experience ▁in ▁the