Preheat the air fryer to 350°F.
Wash, peel, and dice apples into small pieces.
Combine diced apples, lemon juice, white granulated sugar, ¼ teaspoon of cinnamon, and maple syrup together in a bowl.
Butter 4 ramekins and spoon apple mixture into each ramekin.
Air fry for 15 minutes or until apples are cooked through.
In a bowl, mix together butter, brown sugar, oats, flour, and cinnamon.
Top apples with oatmeal topping and cook for another 5 minutes.
Apple crisp is best enjoyed warm with a scoop of vanilla ice cream.