Preheat air fryer to 375°F for 3 minutes and coat the fryer basket with cooking spray.

Separate onion slices into rings and toss with onion powder, 1/2 teaspoon garlic powder, and 1/4 teaspoon salt in a large bowl.

Whisk eggs, flour, and 1/2 cup buttermilk in a shallow dish.

Place panko in another shallow dish.

Dip each onion ring in the egg mixture, allowing excess to drip off, then dredge in panko to coat completely; place in the fryer basket.

Repeat until the basket is full and coat the onion rings with cooking spray.

Cook, flipping once, until crispy, about 8 minutes. Repeat with the remaining onion rings in batches as needed.

Meanwhile, whisk mayonnaise, chives, parsley, remaining 1/4 cup buttermilk, and remaining 1/2 teaspoon garlic powder in a small bowl.

Sprinkle the onion rings with the remaining 1/4 teaspoon salt and serve with the dipping sauce.