Why battleships carried their own spotting aircraft

How well could one ship's aircraft spot gunfire for another ship?

It could be done, but assigning a dedicated aircraft to each firing ship greatly reduced confusion.

Spotting for another ship was possible, but the observer had to identify that ship's splashes, target, manoeuvres, and sometimes torpedo tracks amid a crowded action. A dedicated aircraft simplified the information problem because it followed one firing ship and one correction circuit. Its altitude also gave a clearer view of fall of shot than observers near the waterline. The practice reflects the communications and identification limits of analogue fleet gunnery rather than an assumption that aircraft could not cooperate.