Aerial Volley — ruling 1

You choose how many targets Aerial Volley has and how the damage is divided as you cast the spell. Each target must receive at least 1 damage.

Aerial Volley — ruling 2

If some (but not all) of the targets become illegal before Aerial Volley tries to resolve, the original division of damage still applies, but no damage is dealt to illegal targets. If all targets become illegal, Aerial Volley won't resolve.

Aerial Volley : règles, fonctionnement et interactions (MTG)

Aerial Volley is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Aerial Volley deals 3 damage divided as you choose among one, two, or three target creatures with flying.

How it works : Aerial Volley

Original English text — Wizards of the Coast / Scryfall

#1June 22, 2015· Wizards of the Coast
You choose how many targets Aerial Volley has and how the damage is divided as you cast the spell. Each target must receive at least 1 damage.
No other card is named in this ruling.
#2June 22, 2015· Wizards of the Coast
If some (but not all) of the targets become illegal before Aerial Volley tries to resolve, the original division of damage still applies, but no damage is dealt to illegal targets. If all targets become illegal, Aerial Volley won't resolve.
No other card is named in this ruling.