In a large bowl of ice water, place sweet potatoes. Let stand for 1 hour; drain, rinse, and dry thoroughly.
If preheating is recommended by your air fryer manual, preheat fryer to 400°. Spray basket with cooking spray.
Preheat oven to 200°.
In a large bowl, toss together sweet potatoes, cornstarch, 2 tablespoons oil, and 1 tablespoon Cajun seasoning. Place sweet potatoes in a single layer in air fryer basket. Cook until golden and crisp, 14 to 16 minutes, shaking basket and turning halfway through cooking. Transfer to a rimmed baking sheet, and keep warm in oven. Repeat until all sweet potatoes are cooked.
Notes
Kitchen Tip: Cornstarch helps make these sweet potato fries extra crispy.