I tried doing the math from Boeing's stated fuel economy for different models of planes and even older 747s which aren't great in terms of fuel economy were com

I tried doing the math from Boeing's stated fuel economy for different models of planes and even older 747s which aren't great in terms of fuel economy were coming out 2.5x better than the numbers in this article. I can't figure out how they are coming up with their numbers. Maybe there are lots of empty planes on these routes or something?