Why shorter fuselage aircraft could fly longer ranges than longer fuselage aircraft?

I'm talking about the Boeing 747SP which could fly further than it's longer fuselage brothers 747-100/200/300. That was before the 747-400 with its winglets on the wingtips entered service in 1989 which now could fly further than its older 100/200/300/SP version brothers and the new 747-8 could fly even... show more I'm talking about the Boeing 747SP which could fly further than it's longer fuselage brothers 747-100/200/300. That was before the 747-400 with its winglets on the wingtips entered service in 1989 which now could fly further than its older 100/200/300/SP version brothers and the new 747-8 could fly even further but the 747SP still is the highest flying subsonic commercial aircraft at an altitude of 45100 feet.
8 answers 8