Begin by patting the chicken legs dry with a paper towel to remove any excess moisture. This helps the seasoning adhere better.
In a large zip-top bag, combine the brown sugar, kosher salt, ground black pepper, ground mustard, onion powder, garlic powder, smoked paprika, and cayenne pepper. Shake the bag well to mix all the dry ingredients thoroughly.
Add the chicken legs to the bag, pour in the vegetable oil, and shake until each leg is evenly coated with the seasoning mixture.
Preheat your air fryer to 380°F for about 5 minutes. Once preheated, arrange the seasoned chicken legs in the air fryer basket.
Set the air fryer to the air fry setting at 380°F and cook the chicken for 18-22 minutes, making sure to turn the legs halfway through the cooking time. The chicken is done when the internal temperature, measured with an instant-read thermometer, reaches between 165°F and 185°F.
Enjoy your perfectly seasoned, crispy, and juicy air fryer chicken legs!