To kill it without flyers, Get a strong velonasaur and bring it up to the titan flying by using the geysers. Once on top shred it with the right click attack, when you are about to fall on the titan or it knocks you off, just dismount before you hit the ground. Rince and repeat. Kill the flock before it dismounts you.
Pro tip: Don't use explosive weaponry and really bad rexes with no saddles like the devs did. Fab Snipers for taming it with little/no collateral damage, actually decent rexes + imprint + saddles to kill it (Probably not for this flying one tho lmao).