I have an older "convection" wall oven which I think probably has something like a $10 fan added to a regular oven BOM. From what I can tell if you put the item to be cooked on a cooling rack set in a baking tray, you have something close enough to an air fryer to be no different. Of course, people in small apartments have had toaster ovens forever so maybe an air fryer is just the modern replacement for that.