Vigilance
Whenever Thunderous Orator attacks, it gains flying until end of turn if you control a creature with flying. The same is true for first strike, double strike, deathtouch, indestructible, lifelink, menace, and trample.
Check the creatures you control as the triggered ability resolves to determine which abilities Thunderous Orator gains. Once Thunderous Orator gains an ability, it doesn’t matter what happens to other creatures you control with that ability.
If you control a creature with one of the abilities listed in the last sentence, Thunderous Orator will gain the that ability, not flying.