Preheat the air fryer to 350° F. Grease a 6x6-inch baking dish with butter.
In a medium bowl, combine the milk, eggs, brown sugar, maple syrup, vanilla, and cinnamon; whisk until fully combined.
Add half of the cubed bread to the baking dish to the bottom of the baking dish in an even layer, followed by half of the peaches and blueberries. Top with the second half of the bread and remaining fruit. Pour the milk mixture over the bread and fruit, then gently press with a spatula to ensure that the bread is soaked. Set aside for 10 minutes.
Cover the baking dish with foil and place it into the air fryer basket, cooking for 30 minutes. Remove the foil from the dish and cook for 10 more minutes uncovered. Let sit for 10 minutes before serving.