Plumecreed Mentor

Flying
Whenever Plumecreed Mentor or another creature you control with flying enters, put a +1/+1 counter on target creature you control without flying.

Lofty Denial

Counter target spell unless its controller pays {1}. If you control a creature with flying, counter that spell unless its controller pays {4} instead.

Winged Words

This spell costs {1} less to cast if you control a creature with flying.
Draw two cards.

Plains

Elite Guardmage

Flying
When Elite Guardmage enters, you gain 3 life and draw a card.

Aerial Assault

Destroy target tapped creature. You gain 1 life for each creature you control with flying.

Island

Tide Skimmer

Flying
Whenever you attack with two or more creatures with flying, draw a card.

Falconer Adept

Whenever Falconer Adept attacks, create a 1/1 white Bird creature token with flying that's tapped and attacking.

Dazzling Denial

Counter target spell unless its controller pays {2}. If you control a Bird, counter that spell unless its controller pays {4} instead.

Empyrean Eagle

Flying
Other creatures you control with flying get +1/+1.

Watcher of the Spheres

Flying
Creature spells with flying you cast cost {1} less to cast.
Whenever another creature you control with flying enters, Watcher of the Spheres gets +1/+1 until end of turn.

Koilos Roc

Flash
Flying
When Koilos Roc enters, create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")

Warden of Evos Isle

Flying
Creature spells with flying you cast cost {1} less to cast.

Aether Channeler

When Aether Channeler enters, choose one —
• Create a 1/1 white Bird creature token with flying.
• Return another target nonland permanent to its owner's hand.
• Draw a card.