Set air fryer to 390° Fahrenheit and allow air fryer to preheat 5 minutes. After 5 minutes, remove basket from air fryer and lightly spray basket with spray oil.
Place 2 6-ounce frozen salmon fillets skin-side down in air fryer basket, then return basket to air fryer. Air fry salmon 6 minutes or until just defrosted.
While salmon cooks, add 1 tablespoon olive oil, 1 teaspoon Dijon mustard, 2 teaspoons honey, 1 tablespoon fresh lemon juice, 1 clove garlic, ½ teaspoon salt, and ¼ teaspoon freshly cracked black pepper to medium mixing bowl. Whisk ingredients together vigorously until fully incorporated.
Once salmon has defrosted, carefully remove basket from air fryer. Brush honey-dijon glaze generously onto tops of salmon fillets.
Return basket to air fryer. Air fry salmon 7 minutes more, then check doneness of salmon fillet with internal meat thermometer. If needed, air fry salmon 1 to 2 minutes more or until desired internal temperature is achieved (see Notes).
When satisfied with temperature of salmon fillets, remove salmon from air fryer basket and place on serving plates. Let salmon rest 3 to 5 minutes, then serve salmon with desired sides.