That's not it; Jumpluff, Vespiquen, Butterfree, Scyther, Masquerain, Carnivine et al. are weak to flying as well.
And as for Gyarados, I don't understand why they included it when Gengar is not included, most likely because it loses Levitate when it Mega-evolves, and Gyarados loses its Flying typing when Mega-evolving.