DERG
If you look at a video on youtube of the B787 testing ...as the 'plane rotates..ahem..takes off from the ground you see the wings BEND.
Yes, that's because the fuselage doesn't produce any significant lift so it weighs down the mid-section of the plane, the wings on the other hand are lifting so you get a bend. The wing gets progressively more flexible at the tips so you get more flexing there.
Then we have all the other wing shapes too...like the old Delta wings on our V bombers here in the UK and same as Concorde.
A delta is a naturally more rigid structure than a swept wing as I understand it. I think it has something to do with the fact that by having no trailing edge aft sweep you naturally get less flexing because more of the overall wing's chord connects to the fuselage.
I am sure they did bend a little but nothing like we see now with the B787 or the A380 or that huge Antolov Russian transport 'plane.. Do you agree?
Most larger spans flex more than smaller ones; also most modern airliners use composites much more frequently in the design. They can flex more than metals can and maintain structural integrity if I recall.