Preheat your air fryer to 400°F (200°C) for about 5 minutes.
In a mixing bowl, whisk together the flour, eggs, milk, and salt until you have a smooth batter. Let the batter rest for about 15-20 minutes. This resting period allows the flour to absorb the liquid and improves the rise.
While the batter is resting, grease the cups of a muffin pan with cooking spray. You can use a traditional 12-cup muffin pan or a specialized Yorkshire pudding pan.
Place a small amount of vegetable oil or beef drippings into each muffin cup. Heat the pan in the air fryer for a few minutes until the oil is hot and sizzling.
Carefully pour the rested batter into each muffin cup, filling them about halfway.
Place the muffin pan with the batter-filled cups into the preheated air fryer. Cook at 400°F (200°C) for 15-20 minutes or until the Yorkshire puddings are puffed up, golden brown, and crispy on the outside.
Remove the Yorkshire puddings from the air fryer and serve them immediately while they're hot and at their puffiest.