▁has ▁expanded ▁the ▁number ▁of ▁potential ▁C AT ▁II ▁run ways . ▁ ▁In ▁each ▁case , ▁a ▁suit ably ▁equ ipped ▁aircraft ▁and ▁appropri ately ▁qualified ▁crew ▁are ▁required . ▁For ▁example , ▁C AT ▁III b ▁requires ▁a ▁fail - oper ational ▁system , ▁along ▁with ▁a ▁crew ▁who ▁are ▁qualified ▁and ▁current , ▁while ▁C AT ▁I ▁does ▁not . ▁A ▁H UD ▁that ▁allows ▁the ▁pilot ▁to ▁perform ▁aircraft ▁man eu vers ▁rather ▁than ▁an ▁automatic ▁system ▁is ▁considered ▁as ▁fail - oper ational . ▁A ▁H UD ▁allows ▁the ▁flight ▁crew ▁to ▁fly ▁the ▁aircraft ▁using ▁the ▁guidance ▁c ues ▁from ▁the ▁I LS ▁sens ors ▁such ▁that ▁if ▁a ▁safe ▁landing ▁is ▁in ▁doubt , ▁the ▁crew ▁can ▁respond ▁in ▁an ▁appropriate ▁and ▁tim ely ▁manner . ▁H UD ▁is ▁becoming ▁increasing ly ▁popular ▁with ▁" fe eder " ▁air lines ▁and ▁most ▁manufact ur ers ▁of ▁regional ▁j ets ▁are ▁now ▁offering ▁H UD s ▁as ▁either ▁standard ▁or ▁optional ▁equipment . ▁A ▁H UD ▁can ▁provide ▁cap ability ▁to ▁take ▁off ▁in ▁low ▁visibility . ▁ ▁Some ▁commercial ▁aircraft ▁are ▁equ ipped ▁with ▁automatic ▁landing ▁systems ▁that ▁allow ▁the ▁aircraft ▁to ▁land ▁without ▁transition ing ▁from ▁instruments ▁to ▁visual ▁conditions ▁for ▁a ▁normal ▁landing . ▁Such ▁aut ol and ▁operations ▁require ▁special ized ▁equipment , ▁procedures ▁and ▁training , ▁and ▁involve ▁the ▁aircraft , ▁air port , ▁and ▁the ▁crew . ▁Aut ol and ▁is ▁the ▁only ▁way ▁some ▁major ▁air ports ▁such ▁as ▁Charles