The spell says:
The servant springs into existence in an unoccupied space on the ground within range.
Does the servant need to stay on the ground, or can it move through the air?
Ideally I'm looking for rules-as-written, although since the spell definition does not explicitly say, it would be reasonable to perhaps reference other rules than the spell. Interpretative answers, answers referencing previous editions or lore, or from personal experience might be useful.