If an Aarakocra Druid is flying and casts Gust of Wind, how high is it?

@JeremyECrawford If an Aarakocra Druid is flying and casts Gust of Wind, how high is it? Spell mentions length and width (60' and 10') but not height. Can it affect ground-based foes if the caster is mid-air?

— James Andrew Knight (@jamesaknight1) February 19, 2018

When you cast a spell like gust of wind, you decide its direction. For example, if you're mid-air, you could cast the spell toward the ground, the wind reaching up to 60 feet away from you. #DnD https://t.co/ml5w2FskB4

— Jeremy Crawford (@JeremyECrawford) February 22, 2018

Rephrased: if, standing on the ground, I cast the spell horizontally / straight ahead / parallel to the ground, would a creature flying 5 ft off the ground be affected? 10 ft off the ground? 20 ft? 30 ft?

— Eric Dittert (@EDittert) February 22, 2018

If a spell's area of effect is a line and that line has only width and length, it's a plane. The spellcaster decides how to angle that plane. #DnD https://t.co/S0irczU0HE

— Jeremy Crawford (@JeremyECrawford) February 22, 2018

You decide how to angle it, so yes.

— Jeremy Crawford (@JeremyECrawford) February 22, 2018