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.