Preheat your air fryer to 375 degrees F for 3 to 4 minutes. While it heats, combine the ground turkey, breadcrumbs, Parmesan, egg, garlic, Italian seasoning, salt, and pepper in a large bowl. Mix with your hands until just combined. Do not overwork it or the meatballs will be tough.

Wet your hands lightly under the tap, then roll the mixture into balls about 1 1/2 inches across. You should get 18 to 20 meatballs. Set them on a plate as you go. Wet hands keep the meat from sticking and help you roll without pressing too hard.

Lightly brush or mist the air fryer basket with olive oil. Arrange the meatballs in a single layer with a little space between each one. Work in batches if your air fryer is on the smaller side. Do not stack them or they will steam instead of brown.

Air fry at 375 degrees F for 11 to 13 minutes, shaking the basket gently once at the halfway point. They are done when the outside is lightly browned and the internal temperature reads 165 degrees F on an instant-read thermometer. They should feel firm but not hard when you press one lightly.

While the meatballs cook, warm the marinara in a medium saucepan over medium-low heat, stirring occasionally. If you are serving over pasta, cook the spaghetti according to package directions at the same time.

Add the finished meatballs to the saucepan and turn them gently to coat in the sauce. Let them sit in the warm marinara for 2 to 3 minutes before serving. This helps the flavors come together and keeps the meatballs moist. Serve over spaghetti or pile into hoagie rolls with extra sauce and a sprinkle of Parmesan.