Preheat the air fryer to 400°F (200°C) for 3–5 minutes. A hot basket helps everything crisp faster.
Start the fries.
Add a single layer of frozen fries to the basket. Spritz lightly with oil. Air fry for 8–10 minutes, shaking once halfway, until they start to brown.
Make room for the fish.
Slide the fries to one side or transfer them to a plate and cover loosely with foil. Add the frozen fish fillets to the basket in a single layer. Don’t overlap.
Air fry the fish at 400°F (200°C) for 6–8 minutes.
Spritz the tops with oil for extra crunch.
Flip and finish together. Flip the fish. Return the fries to the basket if you removed them, or spread them back out.
Air fry another 6–8 minutes, shaking the fries once. The fish should be golden and crisp.
Check doneness. Fish is done when it flakes easily and reaches an internal temp of 145°F (63°C).
Fries should be browned with crisp edges. Add 1–2 more minutes if needed.
Season and serve. Sprinkle salt and pepper right away.
Add lemon wedges and tartar sauce. Serve hot.