Welkin Tern

Flying (This creature can't be blocked except by creatures with flying or reach.)
Welkin Tern can block only creatures with flying.

Island

Favorable Winds

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

Hypnotic Siren

Bestow {5}{U}{U} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Flying
You control enchanted creature.
Enchanted creature gets +1/+1 and has flying.

Vaporkin

Flying
Vaporkin can block only creatures with flying.

Windstorm Drake

Flying
Other creatures you control with flying get +1/+0.

Gust of Wind

This spell costs {2} 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.

Winged Words

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

Nimbus Naiad

Bestow {4}{U} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Flying
Enchanted creature gets +2/+2 and has flying.

Sphinx of Magosi

Flying
{2}{U}: Draw a card, then put a +1/+1 counter on Sphinx of Magosi.

Tide Skimmer

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

Aerial Guide

Flying
Whenever Aerial Guide attacks, another target attacking creature gains flying until end of turn.