Skyblinder Staff

Equipped creature gets +1/+0 and can't be blocked by creatures with flying.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Wonder

Flying
As long as Wonder is in your graveyard and you control an Island, creatures you control have flying.

Mu Yanling, Sky Dancer

+2: Until your next turn, up to one target creature gets -2/-0 and loses flying.
−3: Create a 4/4 blue Elemental Bird creature token with flying.
−8: You get an emblem with "Islands you control have '{T}: Draw a card.'"

Reliquary Tower

You have no maximum hand size.
{T}: Add {C}.

Archetype of Imagination

Creatures you control have flying.
Creatures your opponents control lose flying and can't have or gain flying.

Kykar, Wind's Fury

Flying
Whenever you cast a noncreature spell, create a 1/1 white Spirit creature token with flying.
Sacrifice a Spirit: Add {R}.

Isperia the Inscrutable

Flying
Whenever Isperia the Inscrutable deals combat damage to a player, choose a card name. That player reveals their hand. If a card with the chosen name is revealed this way, search your library for a creature card with flying, reveal it, put it into your hand, then shuffle.