In a bowl, marinate chicken with buttermilk, salt, and pepper for at least 15 minutes.
In another bowl, mix cornstarch and flour. Dredge each chicken piece in the dry mix.
Preheat the air fryer to 400°F (200°C). Spray chicken with oil and place in the basket.
Air fry for 10-12 minutes, shaking halfway through, until golden and crispy.
In a small bowl, whisk together mayo, sweet chili sauce, sriracha, and honey to make the Bang Bang sauce.
Toss the crispy chicken in the sauce or serve on the side for dipping.
Garnish with chopped green onions and sesame seeds if desired.