Combine chili powder, paprika, cumin, onion powder, garlic powder, salt, and black pepper in a small bowl and stir with a fork to form the seasoning.
In a large bowl, place the chicken strips, sliced onions, and bell peppers, then drizzle with olive oil and mix thoroughly. Sprinkle the seasoning over and toss to cover everything evenly.
Transfer the seasoned mixture into the air fryer basket.
Set the air fryer to 350 degrees Fahrenheit and cook the mixture for 16 to 20 minutes, shaking or stirring the contents halfway through at around 9 minutes to promote even cooking.
Once cooked thoroughly, spoon the fajita mix into tortillas and top with sour cream, guacamole, and optional chopped cilantro before serving.