▁p umps ▁when ▁fuel ▁output ▁pressure ▁is ▁low , ▁to ▁prevent ▁them ▁from ▁he ating ▁( since ▁they ▁rely ▁on ▁the ▁fuel ▁itself ▁for ▁cool ing ). ▁The ▁other ▁en rich es ▁the ▁nit ro gen ▁levels ▁in ▁the ▁air ▁in ▁the ▁fuel ▁tank , ▁so ▁there ▁is ▁ins u fficient ▁o xygen ▁there ▁for ▁burning . ▁The ▁aircraft ▁engines ▁are ▁also ▁capable ▁of ▁getting ▁fuel ▁via ▁su ction ▁in ▁the ▁result ▁of ▁a ▁failure ▁in ▁the ▁backup ▁p umps , ▁though ▁this ▁produces ▁less ▁reliable ▁thrust . ▁ ▁P lacement ▁ ▁On ▁passenger ▁plan es , ▁fuel ▁t anks ▁are ▁often ▁integrated ▁into ▁the ▁wings , ▁and ▁when ▁there ▁are ▁also ▁t anks ▁inside ▁the ▁body ▁of ▁the ▁aircraft , ▁the ▁wing ▁t anks ▁are ▁used ▁prefer entially . ▁The ▁pla cement ▁reduces ▁the ▁stress ▁on ▁the ▁wings ▁during ▁take off ▁and ▁flight , ▁by ▁putting ▁the ▁heavy ▁fuel ▁directly ▁inside ▁the ▁source ▁of ▁lift . ▁ ▁Put ting ▁t anks ▁in ▁the ▁main ▁wings ▁rather ▁than ▁near ▁the ▁tail ▁or ▁nose ▁also ▁reduces ▁the ▁amount ▁of ▁weight ▁that ▁is ▁off - center ▁from ▁the ▁plane ' s ▁center ▁of ▁gravity , ▁and ▁which ▁changes ▁as ▁it ▁f lies ▁and ▁which ▁would ▁make ▁the ▁aircraft ▁less ▁efficient ▁by ▁requiring ▁increased ▁use ▁of ▁elev ators . ▁Given ▁their ▁irregular ▁shape ▁and ▁lack ▁of ▁windows , ▁wings ▁are ▁often ▁unus able ▁for ▁storage ▁of ▁cargo ▁or ▁se ating ▁of ▁passengers . ▁But ▁their ▁h ollow ▁structure ▁makes ▁in - wing ▁fuel ▁storage ▁feas ible