Scrub and chop sweet potato. Add sweet potato chunks to the preheated air fryer and spray with avocado oil and season with salt and pepper. Airfry for about 20 minutes or until lightly soft.
While cooking sweet potatoes, in a large pan add bacon and cook for a few minutes until crispy. Once cooked, take out bacon, set aside and add onion and garlic to the same pan. Sauté onion and garlic in the bacon grease for 3 minutes or until onion is soft.
In a large bowl, whisk eggs, egg whites, salt, pepper and red pepper flakes.
Layer in the baking dish: sweet potato, onion/garlic mixture, peas, bacon, and feta. Then, carefully pour egg mixture over top.
Cover with foil and bake at 350 for 40 mins. Remove foil and bake another 15 min until quiche is fully set.