You can use any combo of small crackers for a nice variety. Mini Ritz, Chees Its, Mini Saltines, etc. If using the optional extra seasoning and it is salty, make sure to reduce the ranch seasoning by a Tablespoon or so.
Combine the oil and seasonings (ranch seasoning, red pepper flakes, garlic powder, onion powder, dried parsley, and optional extra seasoning) together. Mix until well combined.
Put the oyster crackers in a gallon zip lock bag or similar. Pour the oil/seasoning mix over the crackers.
Close the bag and gently turn and tumble until all the crackers are well coated with the seasoning.
Place the seasoned crackers in the air fryer basket/tray and spread into an even layer (if you have a smaller air fryer (2-3 qt.), you might need to air fry in batches).
Air Fry at 300°F (150°C) for 5 minutes. Shake and turn the crackers.
Continue to Air Fry at 300°F (150°C) for 2-5 minutes or until golden.