Peel the russet potatoes and use a spiralizer to cut them into long curly spirals. If any pieces come out excessively long, cut them with scissors into manageable lengths of about 4 to 5 inches.
Soak the spiralized potatoes in a large bowl of cold water for at least 20 minutes. This removes excess starch and is the secret to achieving truly crispy fries. Drain completely and dry them very thoroughly with clean kitchen towels, pressing firmly to remove all moisture.
In a small bowl, mix together the smoked paprika, garlic powder, onion powder, cumin, cayenne pepper, salt, black pepper, and cornstarch. The cornstarch gives the outside of the fries an extra-crispy crunch.
Place the dried potato spirals in a large bowl. Drizzle with olive oil and toss well, then sprinkle the seasoning mixture over them and toss again until every curl is evenly coated.
Preheat the air fryer to 390 degrees F. Spread the curly fries in the basket in a loose, even layer. Do not pack them tightly. Work in two batches for the best results.
Air fry for 12 to 15 minutes, shaking the basket thoroughly every 4 to 5 minutes, until the fries are golden brown and crispy throughout. Thinner curls will cook faster, so pull out any that are done early to avoid burning.
Season with an extra pinch of salt immediately after cooking and serve hot alongside your favorite dipping sauce.