Lightly grease a loaf pan with cooking spray. Set aside.
In a bowl, add the beef, onion, thyme, breadcrumbs, egg, salt, and black pepper and with your hands, mix until well combined.
Place the beef mixture into the prepared loaf pan and with the back of spoon, smooth the top surface.
Arrange the mushroom slices on top and gently press each inside the meatloaf.
Coat the meatloaf with oil.
Slide the Air Fryer Basket inside and adjust the temperature to 392 °F to preheat for 5 minutes.
After preheating, arrange the loaf pan into the Air Fryer Basket.
Slide the basket into Air Fryer and set the time for 25 minutes.
After cooking time is finished, remove the loaf pan from Air Fryer and place onto a wire rack for about 10 minutes before serving.
Cut into desired-sized wedges and serve.