Gust of Wind — ruling 1

To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions (such as that of Gust of Wind). The mana value of the spell remains unchanged, no matter what the total cost to cast it was.

Gust of Wind — ruling 2

Once you announce that you're casting Gust of Wind, no player may take actions until the spell has been paid for. Notably, opponents can't try to change whether you control a creature with flying.

Gust of Wind — ruling 3

Gust of Wind is unaffected if you no longer control a creature with flying after you've cast it.

Gust of Wind — ruling 4

If the target nonland permanent is an illegal target by the time Gust of Wind tries to resolve, the spell won't resolve. You won't draw a card.

Gust of Wind : règles, fonctionnement et interactions (MTG)

Gust of Wind 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

This spell costs less to cast if you control a creature with flying. Return target nonland permanent you don't control to its owner's hand. Draw a card.

How it works : Gust of Wind

Original English text — Wizards of the Coast / Scryfall

#1April 17, 2020· Wizards of the Coast
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions (such as that of Gust of Wind). The mana value of the spell remains unchanged, no matter what the total cost to cast it was.
No other card is named in this ruling.
#2April 17, 2020· Wizards of the Coast
Once you announce that you're casting Gust of Wind, no player may take actions until the spell has been paid for. Notably, opponents can't try to change whether you control a creature with flying.
No other card is named in this ruling.
#3April 17, 2020· Wizards of the Coast
Gust of Wind is unaffected if you no longer control a creature with flying after you've cast it.
No other card is named in this ruling.
#4April 17, 2020· Wizards of the Coast
If the target nonland permanent is an illegal target by the time Gust of Wind tries to resolve, the spell won't resolve. You won't draw a card.
No other card is named in this ruling.