Originally Posted by archae86
High wing aspect ratio is a key element of high L/D design (all your cited examples have it to a degree unknown in commercial aircraft).
Not quite all.
U-2 has a wingspan of 31 m and wing area of 93 square metres. This gives mean chord of about 3 m and aspect ratio of about 10. Which is not unknown for airliners.
Originally Posted by archae86
The impact on civil airfield infrastructure and capacity is one significant barrier.
Perhaps. Though something interesting seems to have happened there.
Boeing 747 used to be the biggest civil plane, with wingspan of 59,6 m. All other widebodies were much smaller - DC-10 and Tristar had wingspan of 47,3 m, A300 and A310 had around 44 m, Il-86 had 48 m, B-767 had 47,6 m, even MD-11 had just 51,7 m and 767-400 has 51,9 m.
But Airbus 330 has a wingspan 60,3 m. Much slimmer than the 747 wing: a 747 wing spans 59,6 m and has area of 511 square metres, while a 330 wing spans 60,3 m and has area of just about 360 square metres. That means mean chord about 6 m and aspect ratio of about 10, like U-2...
The other widebodies seem to have followed suit - B777 wingspan is 60,9 m and Il-96 has 60 m wingspan as well. B787 is supposed to have 60,1 m.
How do airports manage with that?
Also... Tristar and DC-10 are out of production, so are MD-11 and Il-86, A300 and A310 are no longer offered... there is talk of replacing B767 with B787.
This would mean that no aircraft with wingspan between 40 m and 60 m would be produced... what happens to airports built for such kinds of planes? Too small for A330, B777 and B787, while the narrowbodies in production - B737 and A320 - have wingspan of around 35 m... much space wasted in airports built around MD-11 or B767...