Prick sausage links several times with a fork to prevent bursting.
In a bowl, toss sliced bell peppers and onion with olive oil, Italian seasoning, garlic powder, red pepper flakes, salt, and pepper.
Place sausages in air fryer basket and arrange peppers and onions around them.
Air fry at 380°F for 15-18 minutes, shaking basket and turning sausages halfway through, until sausages reach internal temperature of 165°F and vegetables are tender.
Let rest for 2 minutes, then slice sausages and serve with the peppers and onions.