It's funny you mention this. About 3 years ago I was told by a congressional member of the aviation sub-committee that Boeing has the plans to your concept already on the drawing board.

Which airline would be first to order it in a single-aisle, 4x4 configuration?

Why no go for standing room only. Or maybe they will hang some slings from the ceiling where you kind of hang there like rock climbing gear!

When one considers how wide humans have become, and how much wider they most assuredly will get, then a wider tube (and seats) is a no brainer. While steerage in a Bus is tight, steerage in the 737/757 tube is just torture. Unless of course, you're a jockey or fitness bunny.

Edwin Colodny wanted a twin aisle semi narrow body 25 years ago. The idea is long past due. I'm certain that I'll retire before I ever ride on one.

They are replacing all our seats that have padding so they can shoehorn in more slimline park bench seats and you think our management would want an extra aisle where seats could go? Riiiiight.

If the tube was designed and constructed with two aisles and three sets of two seats across, there would be no way to add seats along its width. The can mess with the pitch and legroom all they want, the seats width is much more difficult to change.

Why wouldn't they shrink the 787 to the 200-240 seat range? common type, parts...etc. It's already composite so it'll be lighter (there's your extra range) and it's Way cheaper than starting from scratch,

787SP? 200 Passengers with a range of 10,000 NM? I like your style...

2 aisles with six seats per row would get killed on a cost basis by the standard 3X3 single isle seating. The airframe would be horribly inefficient on a per seat basis. There is a reason almost every airline now is trying to use every sq inch of floor space for more seats.

I believe an old CEO's of ours said of the 767 vs 757:

We need more seats in the airplane, not more aisles.