Where did Hornets and Falcons go?
Content in Halo 5 has been put in via piecemeal updates, and as of right now there are no UNSC flight vehicles. Mabye that will change in time, I don’t know. You can keep up to date on the news with the community updates, but besides that, that’s all that’s known.
Hopefully one of them makes their way back into the game soon. The UNSC needs an air vehicle.