Pre-heat your air fryer to 400°F.
Cut about ½ an inch off the pointing stem of the onion and leave the root intact on the bottom. Peel the skin of the onion all the way and rip it off carefully to leave the root intact. Flip the onion over so that the root is pointing up now. Then, starting about ½ an inch from the root, make a cut all the way down to the cutting board. Do this every inch around the onion, until you have slices going around the whole onion.
Flip the onion over, and the onion should be bloomed. You may have to seperate the tips of the outer onion using your hands.
In a bowl, combine your flour, panko crumbs and old bay seasoning and mix. In a seperate bowl, whisk the eggs and milk together.
Place the onion in the flour, panko crumbs, and old bay seasoning mix, and coat the onion. Make sure to get some in all the layers.
After, place the onion in the eggs and milk mixture and coat the onion. I like to flip the onion while in the mixture to assure that it is all coated.
Return the onion back into the flour, panko crumbs, and old bay seasoning mix and coat one last time. Make sure its well covered. Flip and gently shake to remove any excess flour.
Spray the onion with coooking spray or drizzle oil on it generously, and place it in the air fryer for 20-25 minutes. You are going to have to spray it about two or three times with oil while it is cooking. (if you deep fry the blooming onion, heat oil to 375°F, and cook for 6 minutes, flipping halfway through)
Serve and enjoy!