Generously butter and flour two 9x5x3 loaf pans and preheat your oven to 325°.
In a medium bowl add the flour, baking powder, baking soda and salt, whisk to combine. Then in a smaller bowl, combine the 3 bananas, milk, cinnamon and nutmeg by mashing with a fork. Set both bowls off to the side for a moment.
Next, in the bowl of your mixer, cream together the butter and sugars until light and fluffy, about 2 minutes.
Add in one egg at a time, mixing after each addition. Add the vanilla and banana mixture and mix until just combined.
Gradually add the dry ingredients, mixing on low speed, until incorporated.
Divide batter among the two prepared pans and slide them into your preheated oven. Bake for 35-40 minutes, or until a toothpick comes out clean with only a few crumbs attached. Make sure to rotate the pans halfway throughout baking time.
Allow the bread to cool completely before serving.