Make the optional aioli: Stir together the mayonnaise, garlic, lemon juice, salt, and pepper. Cover and refrigerate for at least 30 minutes to allow the flavors to blend.
Prepare the artichokes: Pat the drained and rinsed artichoke hearts dry with paper towels. Cut them in half and blot the cut sides to remove any remaining moisture.
Mix the coatings: In a shallow bowl, whisk together the flour and water, adjusting with a little more flour or water as needed to reach a thin pancake batter consistency. In another shallow bowl, combine the panko, Parmesan, lemon pepper seasoning, and optional salt.
Coat the artichokes: Dip each artichoke half into the flour mixture, letting the excess drip off. Dredge through the bread crumb mixture until lightly covered.
Prepare the air fryer: Preheat to 370°F and lightly spritz the basket with cooking spray. Working in batches, arrange the artichokes in a single layer, leaving space between the pieces. Spray the tops with cooking spray.
Air fry: Cook for 8 to 10 minutes, flipping halfway through and spraying the other side with cooking spray. The coating should be crispy and golden brown. Repeat with the remaining artichokes.
Serve: Serve warm with the garlic aioli, if desired.