Preheat the air fryer to 400°F for 5 minutes.
Pat the 4 salmon fillets dry with paper towels.
Season the flesh side of each fillet with salt and black pepper to taste.
Drizzle 1 teaspoon olive oil over the flesh of each fillet (use all 4 teaspoons total) and rub to coat evenly.
Place the fillets in a single layer in the air fryer basket, skin side down, without overlapping.
Cook at 400°F for 7 minutes. Check doneness—salmon should be opaque and flake easily with a fork; if needed, cook 1–2 minutes longer.
Carefully remove the fillets from the air fryer and serve immediately.