Add the chili powder, smoked paprika, cumin, garlic powder, onion powder, dried oregano, salt, and black pepper to a small bowl. Stir until evenly combined.
Pat the chicken breasts dry, then slice them into relatively even strips. Slice the bell peppers and onion into similar-sized strips.
Place the chicken, red bell pepper, yellow bell pepper, and onion in a large mixing bowl.
Pour the olive oil over the chicken and vegetables. Toss until everything is lightly and evenly coated.
Sprinkle half of the prepared seasoning mixture over the bowl and toss thoroughly.
Add the remaining seasoning and toss again, making sure the chicken and vegetables are evenly seasoned.
Transfer the mixture to the air fryer basket. Spread the chicken and vegetables as evenly as your air fryer allows.
Cook the Air Fryer Chicken Fajitas at 400°F (204°C) for approximately 15 minutes.
After 10 minutes, open the air fryer and use tongs to toss and turn the chicken, peppers, and onions.
Continue cooking for another 5 minutes, then check the chicken for doneness.
The chicken should reach an internal temperature of 165°F (74°C) in the thickest pieces. If necessary, cook for another 1–3 minutes.
Remove the chicken and vegetables from the air fryer and squeeze fresh lime juice over the top, if desired.
Serve immediately with warm tortillas and your favorite fajita toppings.