▁de ▁Ga ulle ▁Airport ▁remain ▁oper ational ▁every ▁day ▁of ▁the ▁year . ▁Some ▁modern ▁aircraft ▁are ▁equ ipped ▁with ▁en hanced ▁flight ▁vision ▁systems ▁based ▁on ▁inf ra red ▁sens ors , ▁that ▁provide ▁a ▁day - like ▁visual ▁environment ▁and ▁allow ▁operations ▁in ▁conditions ▁and ▁at ▁air ports ▁that ▁would ▁otherwise ▁not ▁be ▁suitable ▁for ▁a ▁landing . ▁Com mer cial ▁aircraft ▁also ▁frequently ▁use ▁such ▁equipment ▁for ▁take offs ▁when ▁take off ▁min ima ▁are ▁not ▁met . ▁ ▁For ▁both ▁automatic ▁and ▁H UD ▁landing ▁systems , ▁the ▁equipment ▁requires ▁special ▁appro val ▁for ▁its ▁design ▁and ▁also ▁for ▁each ▁individual ▁installation . ▁The ▁design ▁takes ▁into ▁consideration ▁additional ▁safety ▁requirements ▁for ▁operating ▁an ▁aircraft ▁close ▁to ▁the ▁ground ▁and ▁the ▁ability ▁of ▁the ▁flight ▁crew ▁to ▁react ▁to ▁a ▁system ▁anom aly . ▁The ▁equipment ▁also ▁has ▁additional ▁maintenance ▁requirements ▁to ▁ensure ▁that ▁it ▁is ▁capable ▁of ▁supporting ▁reduced ▁visibility ▁operations . ▁ ▁Of ▁course ▁nearly ▁all ▁of ▁this ▁pilot ▁training ▁and ▁qual ification ▁work ▁is ▁done ▁in ▁sim ul ators ▁with ▁various ▁degrees ▁of ▁f idel ity . ▁ ▁Use ▁At ▁a ▁controlled ▁air port , ▁air ▁traffic ▁control ▁will ▁direct ▁aircraft ▁to ▁the ▁local izer ▁course ▁via ▁assigned ▁head ings , ▁making ▁sure ▁aircraft ▁do ▁not ▁get ▁too ▁close ▁to ▁each ▁other ▁( m aint ain ▁separation ), ▁but ▁also ▁avoid ing ▁delay ▁as ▁much ▁as ▁possible . ▁Several ▁aircraft ▁can ▁be ▁on ▁the ▁I LS ▁at ▁the ▁same ▁time , ▁several ▁miles ▁apart . ▁An