In a large bowl, combine the ground beef, 3/4 cup crushed Ritz crackers, egg, milk, onion, salt, and black pepper. Mix until just combined.
Shape the mixture into a loaf that fits in your air fryer basket, about 6 inches long and 3 inches high.
Sprinkle the remaining 1/4 cup crushed crackers evenly over the top of the loaf and press lightly to help them stick.
In a small bowl, stir together the ketchup, brown sugar, Worcestershire sauce, and mustard to make the glaze.
Place the meatloaf in the air fryer basket. Cook at 350 degrees for 25 minutes.
Brush the glaze over the top and sides of the meatloaf. Continue cooking for another 10 minutes until the internal temperature reaches 160 degrees and the top looks crispy.
Remove from the air fryer and let rest for 5 minutes before slicing.