Preheat air-fryer to 400 F. Slice onion into rings. In a shallow dish, whisk eggs and milk together. Whisk flour, salt, pepper, and paprika together in another shallow dish.
Place breadcrumbs into another shallow dish. Dip each onion ring in the egg mixture, coat in flour, back into egg, then into the breadcrumbs. Air-fry in batches for 10-12 minutes.