Preheat your air fryer to 200 ℃ (390°F) for a few minutes.
Peel and roughly slice the onions, and set them aside.
Deseed the peppers and slice them the same size as the onions.
Cut the chicken breast into thin, bite sized strips.
In a large mixing bowl, combine the fajita seasoning mix, salt, and, vegetable oil. If you want to make your own fajitas seasoning, simply mix 1 ½ tsp of cumin, 1 ½ tsp of smoked paprika, 1 teaspoon of oregano, ½ teaspoon of garlic powder, and ½ teaspoon of chili together.
Add the chicken strips, along with the sliced peppers and onions.
Toss the mixture to combine and then let it marinate for a couple of hours if you have time.
Place the chicken pieces and vegetables in the air fryer basket, ensuring they are in a single layer without overlapping.
Cook for 10-12 minutes, occasionally tossing with tongs. Make sure to check them at the 5-minute mark and give them a good shake.
When the chicken fajitas are ready, transfer them to a bowl or serve them in tortilla wraps with some sliced jalapeno peppers, sour cream, salsa, coriander leaves, and lime wedges.