Winged Words

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

Steel-Plume Marshal

Flying
Whenever Steel-Plume Marshal attacks, other attacking creatures you control with flying get +2/+2 until end of turn.

Azorius Keyrune

{T}: Add {W} or {U}.
{W}{U}: Azorius Keyrune becomes a 2/2 white and blue Bird artifact creature with flying until end of turn.

Rally of Wings

Untap all creatures you control. Creatures you control with flying get +2/+2 until end of turn.

Donal, Herald of Wings

Whenever you cast a nonlegendary creature spell with flying, you may copy it, except the copy is a 1/1 Spirit in addition to its other types. Do this only once each turn. (The copy becomes a token.)

Kangee, Sky Warden

Flying, vigilance
Whenever Kangee, Sky Warden attacks, attacking creatures with flying get +2/+0 until end of turn.
Whenever Kangee blocks, blocking creatures with flying get +0/+2 until end of turn.

Favorable Winds

Creatures you control with flying get +1/+1.

Stormtide Leviathan

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
All lands are Islands in addition to their other types.
Creatures without flying or islandwalk can't attack.

Empyrean Eagle

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

Jubilant Skybonder

Flying
Creatures you control with flying have "Spells your opponents cast that target this creature cost {2} more to cast."

Prairie Stream

({T}: Add {W} or {U}.)
Prairie Stream enters tapped unless you control two or more basic lands.

Battlefield Raptor

Cloudblazer

Flying
When Cloudblazer enters, you gain 2 life and draw two cards.

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.

Plains

Counterspell

Island

Skycat Sovereign

Flying
Skycat Sovereign gets +1/+1 for each other creature you control with flying.
{2}{W}{U}: Create a 1/1 white Cat Bird creature token with flying.