Preheat your air fryer to 380°F
Slice the chicken breasts into thin strips.
Slice the yellow, green, and red bell peppers, as well as the red onion into strips.
In a large bowl, combine the avocado oil and fajita seasoning together. Add the chicken and vegetables.
Toss or stir to coat the chicken evenly.
Place the seasoned chicken and vegetables in the air fryer basket, spreading them out into a single layer.
Cook in the air fryer for 11 minutes.
Carefully remove the basket and shake it or use tongs to turn the chicken and vegetables.
Cook for an additional 11 minutes, or until the chicken is cooked through and the vegetables are tender.