Pat the chicken thighs dry with paper towels to ensure crispy skin. Season both sides with salt and pepper.
In a small bowl, whisk together honey, Dijon mustard, garlic, and lemon juice or vinegar if using to create the honey mustard sauce.
Lightly brush or spray the chicken thighs with olive oil or cooking spray to help crisp the skin.
Preheat the air fryer to 380°F (193°C).
Place the chicken thighs skin-side down in the air fryer basket in a single layer without overcrowding. Cook for 10-12 minutes.
Flip the chicken thighs and brush with half of the honey mustard sauce. Continue cooking for another 8-10 minutes until internal temperature reaches 165°F (75°C).
Remove the chicken from the air fryer and brush with the remaining honey mustard sauce.
Let the chicken rest for 5 minutes before serving to allow juices to redistribute for moist, tender bites.
Serve with your favorite sides and garnish if desired.