In a large skillet over medium heat, cook the ground beef and diced onion until the beef is browned and the onion is softened, about 7–9 minutes. Drain any excess fat.
Add the cream of mushroom soup, cheddar cheese soup, garlic powder, salt, and pepper. Stir well until the mixture is smooth and creamy.
Preheat the air fryer to 375°F (190°C). Lightly grease an air-fryer-safe casserole dish and spread the beef mixture evenly inside.
Arrange the frozen French fries in a single layer over the beef. Lightly spray the fries with cooking spray for extra crispiness.
Place the dish in the preheated air fryer and cook for 20–25 minutes, until the fries are golden and crisp and the casserole is heated through (beef should reach a safe internal temperature of 160°F / 71°C).
Let the casserole rest a few minutes. Drizzle with ketchup and mustard and garnish with pickles, if desired. Serve with a side salad or your favorite dipping sauce.