Pound the chicken breast to an even thickness of about half an inch to ensure even cooking and tenderization.
Place the chicken in a bowl with the buttermilk and let it marinate for at least 15 minutes to infuse moisture.
In a shallow dish, whisk together the whole wheat flour, garlic powder, onion powder, smoked paprika, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting the excess liquid drip off, then dredge it thoroughly in the seasoned flour mixture.
Lightly coat the chicken on both sides with olive oil spray to help it achieve a golden color in the air fryer.
Place the chicken in the air fryer basket and cook at 375°F for 12-15 minutes, flipping halfway through, until the exterior is golden and crisp.
Toast the whole wheat bun until lightly browned and fragrant.
Spread the Greek yogurt on the bottom bun, then layer with the lettuce, the crispy chicken, and the dill pickles before closing the sandwich.