Not just the window materials but all the aircraft structure that is needed to support the windows to sustain pressurization.

The reason why windows are shaped as they are is to withstand the constant pressure changes without suffering catastrophic fatigue stress failure.

50% of the weight of the bare fuselage. Something was lost in translation when the article was being written.

Any idea how much that is in absolute terms?

Perhaps 100 windows at 10 kg per unit, so roughly one metric ton. The metal required to fill the holes will be quite light. LCD screens are light as well, but less so when you account for the long wires to drive them, plus other infrastructure. Still, you ought to be able to carry a few extra passengers by removing the windows.

No - they're not 'removing' windows, they're building the fuselage without them which eliminates the need for a lot of extra structural reinforcement. This is not just the weight of the windows we're talking about.

Yes, I know. What's your estimate?

> Still, you ought to be able to carry a few extra passengers by removing the windows.

Great! Less legroom but, in return, you get no windows.

It's a fairly easy number to check: Freight aircraft don't have windows or window frames. What is the delta on their empty weight compared to a passenger version?

I'll speculate that a freight 747 is still fundamentally structurally a plane designed to have windows (with the correspondingly reinforced fuselage) but with minor tweaks.

I'd be very surprised if that's not the case. You'd need a plane that's designed from the ground up to not have windows in any configuration.

Still, if the difference is that brutal, there would be a huge niche for planes that have no passenger version and are designed to never have windows.

Not as much as you'd expect. It's easier and cheaper to get a design with windows (and their supporting structure), and not cut out the holes for the windows in the skin. The resulting structure is going to be only marginally lighter, but also much more fatigue resistant. The savings would show up in the changed inspection intervals.

Yes, 50% reduction of the weight of just the fuselage would sound much more plausible.

I'm guessing that

weight with windows - weight without windows = 2 * (weight with virtual windows - weight without windows)

NOT weight with windows = 2 * weight without windows

NOR fuselage weight with windows = 2 * fuselage weight without windows

Yes, total nonsense. See a detailed post by cecilpl2 above.

The net savings is about 1%.