Preheat the air fryer: Set to 390°F (200°C) for 3–4 minutes. A hot basket helps the veggies and chicken sear a bit.
Slice everything evenly: Cut chicken into thin strips, about 1/2-inch thick. Slice peppers and onion into similar widths. Even slices = even cooking.
Mix the spice blend: In a small bowl, combine chili powder, cumin, smoked paprika, garlic powder, onion powder, oregano, salt, and pepper.
Toss chicken and veggies: In a large bowl, add chicken, peppers, and onion. Drizzle with olive oil. Sprinkle the spice blend over and toss until everything is well coated. Add lime zest and half the lime juice.
Air fry in batches if needed: Add a single layer of the mixture to the basket. Don’t overfill. Cook for 10–12 minutes, shaking halfway, until chicken is cooked through (165°F/74°C) and veggies are tender with light char. Repeat with remaining mixture.
Finish with lime: Transfer cooked fajitas to a bowl and squeeze over the rest of the lime juice. Taste and adjust salt if needed.
Warm tortillas: Wrap tortillas in a damp paper towel and microwave 20–30 seconds, or warm in a dry skillet.
Assemble and serve: Fill tortillas with chicken and veggies. Add toppings like cilantro, avocado, salsa, or a dollop of sour cream. Serve immediately.