Preheat your air fryer to 400°F (200°C).

In a large bowl, combine ground chicken, breadcrumbs, egg, onion, bell pepper (if using), garlic, salt, pepper, and thyme. Mix gently until just combined (avoid overmixing).

Gradually add milk or broth, mixing until incorporated. The mixture should be moist but not mushy.

Shape the mixture into a loaf shape on a baking sheet lined with parchment paper.

Brush or spray the top of the meatloaf with oil.

Place the meatloaf in the air fryer basket and cook for 20 minutes.

Flip the meatloaf and cook for an additional 10-15 minutes, or until an instant-read thermometer inserted into the thickest part reaches 165°F (74°C).

Brush with glaze (if using) in the last 5 minutes of cooking for added flavor and browning.

Let the meatloaf rest for 5-10 minutes before slicing and serving.