|Quoting Glareskin (Reply 4):|
Isn't a 757 just a 737 fuselage with higher landing gear because of the bigger engines?
The two share the same fuselage cross section (like say, A300 and A330). The nose, tail, wing boxes, verticle and horizontal stabilizers, and airfoils, as well as landing gear, share nothing in common between the two.
The 757 wing is a 15 year older design, and while it has fantastic lifting abilities (like the 276,000 lbs of 753), my suspicions are that the 73G wing may be slightly more efficient. Moreover, raked wingtip extensions, like those on 764 and 772LR/773ER over the 73G wing could provide the additional lift needed with negligible drag penalty. If they really wanted, they could sling the slightly less efficient, but more powerful CFM56-5C (you know it from the A342 and A343) which has demonstrated up to 36,000lbs of thrust, and is rated to a static 34,000lbs. That and raked wingtip extension, and you could pull a heavier plane, with more fuel, into the air leaving the 757, and it's late 70s/early 80s technology aside, and probably get better economics (given the 739's better structural efficiency vs 752).