▁I cel and ▁said ▁that ▁the ▁production ▁of ▁ash ▁from ▁E y ja f j alla jö k ull ▁was ▁likely ▁to ▁continue ▁at ▁a ▁compar able ▁level ▁for ▁some ▁days ▁or ▁even ▁weeks ; ▁a ▁ge oph ys ic ist ▁at ▁the ▁I cel and ic ▁Meteor ological ▁Office ▁said , ▁" Where ▁it ▁dis rupt s ▁travel ▁depends ▁on ▁the ▁weather . ▁It ▁depends ▁how ▁the ▁wind ▁car ries ▁the ▁ash ". ▁ ▁Jet ▁engine ▁toler ance ▁to ▁air bor ne ▁particles ▁ ▁In ▁ 1 9 8 2 , ▁British ▁Air ways ▁Fl ight ▁ 9 ▁fle w ▁through ▁vol can ic ▁ash ▁of ▁Mount ▁Gal ung g ung , ▁Java , ▁Indones ia , ▁causing ▁all ▁ 4 ▁engines ▁to ▁shut ▁down . ▁However , ▁the ▁crew ▁restart ed ▁all ▁but ▁one ▁of ▁the ▁engines ▁and ▁land ed ▁safely . ▁Sub sequently , ▁there ▁was ▁an ▁addition ▁to ▁the ▁operations ▁manual s , ▁describing ▁how ▁to ▁deal ▁with ▁vol can ic ▁ash . ▁ ▁I cel and ' s ▁authorities ▁had ▁been ▁warning ▁the ▁air lines ▁for ▁several ▁years , ▁asking ▁them ▁to ▁determine ▁the ▁density ▁of ▁ash ▁that ▁is ▁safe ▁for ▁their ▁jet ▁engines . ▁ ▁But ▁before ▁the ▁vol can ic ▁events ▁of ▁April ▁ 2 0 1 0 , ▁aircraft ▁engine ▁manufact ur ers ▁still ▁had ▁not ▁defined ▁specific ▁particle ▁levels ▁above ▁which ▁engines ▁were ▁considered ▁to ▁be ▁at ▁risk . ▁The ▁general ▁approach ▁taken ▁by ▁air space ▁regul ators ▁was ▁that ▁if ▁the ▁ash ▁concentration