To cook a jacket potato (baked potato) in an air fryer, the typical cooking time is about 40 to 60 minutes at 400°F (around 200°C), depending on the size of the potato. Medium-sized potatoes usually take around 40 to 50 minutes, while larger ones may need up to an hour. It is recommended to prick the potato a few times with a fork, rub with olive oil, and sprinkle with salt before cooking. Flipping the potato halfway through cooking helps achieve crispy and evenly cooked skin. The potato is done when it is fork tender inside and the skin is crispy. Some tips:

• Preheat the air fryer to 400°F if your model requires it, although some don't need preheating.
• You can coat the potato skin with oil to get it extra crispy.
• Check the potato around halfway, flip it, and finish cooking.
• Cooking times vary by potato size and model of air fryer, so adjust as needed.

In summary, cooking a jacket potato in an air fryer at 400°F takes roughly 40 to 60 minutes for a crispy skin and fluffy interior.