Using this logic, the space shuttle would be the largest aircraft, would it not? I get it, though, wingspan and takeoff weight are arbitrary methods of gauging an aircraft’s largeness.

I was a crew chief on C-5s, so I’m obviously biased toward wingspan. They’re all big, and it’s a small miracle they can fly in the air at all.

I could be wrong, but I’ve always understood that they measure aircraft size, in terms of wingspan. I’ve never heard of takeoff weight being used as a ranking measure, in terms of size.