Place the chicken breast between two sheets of parchment paper and pound to a uniform 1/2-inch thickness for even cooking.
Submerge the chicken in a bowl with the buttermilk and let it marinate for at least 15 minutes to tenderize.
In a shallow dish, whisk together the whole wheat flour, garlic powder, onion powder, paprika, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting excess drip off, then dredge thoroughly in the seasoned flour mixture until fully coated.
Lightly coat the air fryer basket with half the olive oil, place the chicken inside, and drizzle the remaining oil over the top.
Air fry at 400°F (200°C) for 12-15 minutes, flipping halfway through, until the exterior is golden-brown and the internal temperature reaches 165°F.
Toast the whole wheat bun until warm, then assemble the sandwich with the lettuce, crispy chicken, and pickles.