Wash and scrub sweet potatoes. Pat dry. Peel if desired.
Cut sweet potatoes into ¼–½ inch sticks, keeping them uniform.
Pat cut fries dry again with paper towels.
Place fries in a large bowl. Sprinkle cornstarch over them and toss to coat evenly.
Drizzle oil over fries. Add salt, pepper, and optional seasonings. Toss to coat.
Preheat air fryer to 380°F (193°C) for 3–5 minutes.
Arrange fries in a single layer in the basket. Cook in batches if necessary.
Air fry for 12–15 minutes, shaking or tossing every 5 minutes until golden and crispy.
Serve immediately, seasoning with extra salt if desired.