Place the sliced chicken thighs, bell peppers, and red onion into a large mixing bowl.
Drizzle the olive oil over the mixture and sprinkle in the spicy fajita seasoning, smoked paprika, and salt.
Toss everything well until the chicken and vegetables are evenly coated.
Transfer the mixture to the air fryer basket, spreading it into a single layer if possible.
Air fry at 400°F for 14 minutes, shaking the basket halfway through to promote even browning.
Remove the basket and check that the chicken is cooked through and the vegetables have softened with crisp edges.
Divide the fajita mixture among four plates and finish with a squeeze of lime and a sprinkle of cilantro.