▁thick ness . ▁This ▁reduces ▁the ▁forces ▁in ▁the ▁sp ar ▁by ▁a ▁factor ▁of ▁ 2 ▁x ▁ 2 ▁= ▁ 4 , ▁allowing ▁a ▁four fold ▁increase ▁in ▁the ▁overall ▁load . ▁This ▁exactly ▁matches ▁the ▁increased ▁lift ▁available ▁from ▁the ▁larger ▁wing ▁area . ▁ ▁This ▁means ▁that ▁the ▁metal ▁parts ▁of ▁a ▁large ▁aircraft ▁need ▁be ▁no ▁th icker ▁or ▁heav ier ▁than ▁those ▁of ▁a ▁smaller ▁aircraft . ▁However , ▁because ▁these ▁parts ▁must ▁cover ▁four ▁times ▁the ▁area ▁they ▁make ▁the ▁aircraft ▁four ▁times ▁heav ier . ▁This ▁again ▁exactly ▁matches ▁the ▁increase ▁in ▁l aden ▁weight , ▁so ▁there ▁is ▁no ▁struct ural ▁limit ▁to ▁how ▁large ▁( or ▁small ) ▁an ▁aer op lane ▁can ▁be ▁made . ▁ ▁Lar ge ▁aircraft ▁do ▁still ▁pose ▁a ▁design ▁challenge . ▁The ▁struct ural ▁members ▁may ▁be ▁no ▁th icker , ▁but ▁they ▁are ▁now ▁twice ▁as ▁long , ▁so ▁st iff ness ▁becomes ▁a ▁problem , ▁and ▁the ▁design ▁approach ▁must ▁be ▁adapted ▁to ▁ensure ▁ade qu ate ▁overall ▁st iff ness . ▁This ▁is ▁typically ▁achieved ▁by ▁making ▁struct ural ▁members ▁cell ular . ▁For ▁example , ▁the ▁wing ▁sp ar ▁in ▁a ▁small ▁aircraft ▁may ▁in ▁fact ▁be ▁a ▁simple ▁I - be am ▁with ▁a ▁solid ▁cross - section , ▁but ▁in ▁a ▁larger ▁design ▁the ▁u pr ight ▁part ▁of ▁the ▁beam ▁or ▁" web " ▁will ▁be ▁constructed ▁as ▁an ▁open ▁lattice ▁of ▁tr uss es ▁in ▁a ▁tri ang ulated