What flag is flown while a ship is conducting a signal drill?

The signal drill is conducted with the Sierra flag, which has a specific purpose in maritime communication. This flag, displaying a white field with a blue diagonal stripe, signals "I am complying with regulations" or "I am using the signal flags." Flying the Sierra flag indicates to other vessels that the ship is engaged in signal drills, informing them of the activity taking place. This is crucial for maintaining safe navigation and ensuring that other ships are aware of the drill, reducing the likelihood of misunderstandings at sea.

Other flags in the options serve different communicative roles. Bravo, for instance, signals that the ship is carrying or transferring dangerous cargo, and Alpha indicates that the ship has a diver down and is exercising caution. Therefore, for the specific situation of conducting a signal drill, Sierra is the flag appropriately used to communicate this endeavor to others in close proximity.