Kitesail Corsair has flying as long as it's attacking.
1/19/2018 Kitesail Corsair has flying immediately after it attacks. This means that combat restrictions on creatures with flying (such as that of Sandwurm Convergence) don’t apply, but abilities that trigger on creatures with flying attacking (such as that of Windreader Sphinx) do trigger.
1/19/2018 To determine the total cost of a Dinosaur spell, start with the mana cost or alternative cost you’re paying, add any cost increases, then apply any cost reductions. The converted mana cost of the creature remains unchanged, no matter what the total cost to cast it was.