Each balloon would cover a circle, so it'd be more like 1,250 sq km. I think it would be optimistic to expect each balloon to cover exactly that area. They'd ne

Each balloon would cover a circle, so it'd be more like 1,250 sq km. I think it would be optimistic to expect each balloon to cover exactly that area. They'd need to overlap just to eliminate gaps, and I'm sure there's a random element to their motion, so that would require them to overlap more.