Add olive oil, Dijon mustard, honey, tarragon, garlic powder, and salt to a medium bowl. Stir to combine.
Add chicken breasts to the marinade and mix to evenly coat. Cover with plastic wrap and refrigerate to marinate for at least 30 minutes, or up to 2 hours.
Remove chicken from the refrigerator. Place it in the air fryer basket in a single layer.
Air fry at 370°F for 10 minutes. Flip the chicken and cook for an additional 6-9 minutes for smaller breasts.
Once the chicken reaches an internal temperature of at least 165°F, remove it from the air fryer basket. Let it rest for 5 minutes before slicing.