What term is used to indicate that you have an aircraft within the formation in sight?

The term "Visual" is used to indicate that a pilot has another aircraft within the formation in sight. In formation flying, maintaining visual contact with other aircraft is crucial for safety and coordination. When a pilot calls "Visual," it confirms that they can see the other aircraft and are aware of its position, which helps in maintaining the formation and executing maneuvers effectively.

The other terms carry different meanings. "Blind" indicates that a pilot does not have visual contact with the formation, which is the opposite of being visual. "Tally ho" is typically used during air-to-air engagements to denote sighting an aircraft or target, but it is not the standard term for maintaining sight in a formation. "No Joy" means that the pilot has not seen the designated aircraft or target, similar to "Blind." Thus, "Visual" is the correct and standard terminology for acknowledging sighting another aircraft in formation flying.