Season the chicken. Cut the chicken into small, thin strips or bite-sized pieces for even cooking. In a mixing bowl, toss it with the taco seasoning, olive oil, lime juice, salt, and pepper until evenly coated. For more flavor, marinate 15–30 minutes (or up to overnight).
Preheat. Preheat the air fryer to 380°F (190°C) for 3–5 minutes.
Air fry the chicken. Arrange the chicken in a single layer in the basket — do not overcrowd. Cook for 8–10 minutes, shaking the basket or flipping halfway through, until the edges are golden and the internal temperature reaches 165°F (74°C).
Warm the tortillas. Wrap the tortillas in foil and add to the air fryer for the last 2–3 minutes, or warm them in a dry skillet until pliable.
Assemble. Add a few pieces of chicken to each warm tortilla. Top with diced onion, cilantro, and any optional toppings.
Serve. Finish with crumbled cheese, salsa or hot sauce, and a squeeze of lime. Serve immediately with extra lime wedges on the side.