Grass, Bug, and Fighting-type Pokemon are weak against Flying-type moves, which causes it to receive double the damage from Flying-types.
There are 22 flying-type Pokemon.
Flying type Pokemon are good against normal Pokemon.
Swanna is a Water and Flying type pokemon.
Crobat is a Poison and Flying type pokemon.
Find a Flying-type Pokemon and catch it. There are plenty of them in each game and many Flying-type Pokemon are common Pokemon, so you shouldn't have trouble doing so.
The weakness of flying type Pokemon is Ice, Electric and Rock.
Jumpluff is a Grass and Flying type pokemon.
The LARGEST Flying Pokemon is RAYQUAZA at 23' (7m) in length.
You could check Serebii.net for a list of flying Pokemon. It would be under the DPPt PokeDex.
Thundurus is an Electric and Flying type pokemon.
with a flying pokeball
flying Pokemon