Preheat the air fryer to 380°F.
Place the 6 medium potatoes (or 4 large potatoes) — scrubbed and cut into 1/4-inch sticks — in a large bowl. Drizzle with 2 tablespoons olive oil and sprinkle with 1 teaspoon salt. Toss until the fries are evenly coated.
Arrange a single layer of fries in the air fryer basket, leaving space between pieces so air can circulate. Work in batches as needed to avoid overcrowding.
Air fry the first batch at 380°F for 15–18 minutes, shaking the basket or turning the fries once about halfway through cooking to promote even browning.
Remove the cooked fries to a plate or baking sheet and repeat steps 3–4 with the remaining fries.
When all batches are cooked, return all fries to the air fryer basket in a single layer (or as close to a single layer as possible) and air fry for an additional 2–3 minutes at 380°F to reheat and crisp them.
Remove the fries from the air fryer and serve immediately.