Preheat oven to 350 degrees F (175 degrees C). Lightly grease two 9 x 5 inch loaf pans.
In a large bowl, cream together the shortening and sugar until light and fluffy. Stir in the eggs one at a time, beating well with each addition. Stir in the mayonnaise and bananas. Stir together the flour, baking powder, baking soda, and salt. Blend the flour mixture into the banana mixture; stir just enough to evenly combine. ALTERNATE: fold in the chocolate chips and walnuts.
Bake at 350 Degrees until a toothpick inserted into the center of the loaf comes out clean, about 50 to 75 minutes. Cool loaf in the pan for 20 minutes before removing to a wire rack to cool completely.