Combine all ingredients for cinnamon swirl and mix with pastry cutter or fork until it resembles small crumbs.
Pour half of banana bread batter into prepared loaf pan.
Sprinkle cinnamon sugar swirl crumbs on top of batter.
Pour remaining batter over crumbs.
Bake for 60-70 minutes. Check after 30 minutes to make sure top is not getting overly brown. If so, cover loosely with aluminum foil.
Test for doneness by inserting toothpick in center of bread. It is done if it comes out clean. Remove from oven to wire rack to cool for 15 minutes. Remove from loaf pan and finish cooling on rack.