Preheat the air fryer to 400°F (200°C) for 5 minutes.
Pat the salmon fillets dry with paper towels.
Brush both sides of the salmon fillets with 1/2 tablespoon olive oil.
Season the salmon fillets evenly with 1/4 teaspoon salt, 1/8 teaspoon black pepper, and garlic powder.
Place the salmon fillets skin-side down in the air fryer basket, making sure they do not overlap.
Cook the salmon in the air fryer for 10 to 12 minutes, or until the internal temperature reaches 145°F (63°C) and the salmon flakes easily with a fork.
While the salmon cooks, heat the remaining 1/2 tablespoon olive oil in a large skillet over medium heat.
Add the minced garlic and sauté for 30 seconds until fragrant.
Add the chopped Swiss chard leaves and cook, stirring frequently, for 4 to 5 minutes until wilted and tender.
Season the Swiss chard with the remaining 1/4 teaspoon salt, 1/8 teaspoon black pepper, lemon juice, and crushed red pepper flakes if using. Stir to combine.
Remove the salmon from the air fryer and let rest for 2 minutes.
Serve the salmon fillets alongside the sautéed Swiss chard.