I am seeing several responses suggesting to add wheat gluten.
The gluten content in the dough isnβt directly what makes the bread fluffy.
The gluten strands are what keep the cell structure of the bread together. So if the gluten is βstrongβ it will hold the cell structure while the dough is rising and that will give it the fluffiness when it bakes.
So yes, more gluten would do it, but also working with the gluten you have and not damaging it helps.