[Mika]

Gyarados was always water flying. Ever since the very first games.
He can learn dragon rage, and twister and some other dragon moves, but he is water flying.

Charizard was intentionally not given dragon type status due to the fact having a dragon type starter pokemon would be horribly unfair. Even though it isn't a starter in the new games, starter pokemon have certain stat ranges. As all pokemon do. Charizard would be a pseudolegendary with dragon status.