There are a few things to keep in mind when it comes to cooking filet mignon in an air fryer.  First of all, the thickness and size of the air fryer steak will impact the cooking time.  A 1-inch steak will take about 6 to 8 minutes to cook through, while a 1.5-inch steak will take closer to 8 to 10 minutes.  Secondly, you'll want to make sure that your air fryer is preheated before adding the steak. This will help to ensure that the steak cooks evenly.  Finally, be sure to use an instant-read thermometer to check the internal temperature of the steak before removing it from the air fryer.  This will ensure that your steak is perfectly cooked to your liking.