Shmita is a law of the land of Israel, not of the airspace above it.
A proof is that plants grown through hydroponics, i.e., with their roots outside of the soil, are not subject to the restrictions of Shmita (see e.g., here footnote 12 and there question 4).
Also, the biblical source for shmita speaks explicitly of the land
Six years you shall sow your land and gather in its yield; but in the
seventh you shall let it rest and lie fallow. (Shemot 23:10-11)
When you enter the land that I assign to you, the land shall observe a
sabbath of the Lord. Six years you may sow your field and six years
you may prune your vineyard and gather in the yield. But in the
seventh year the land shall have a sabbath of complete rest, a sabbath
of the Lord: you shall not sow your field or prune your vineyard. You
shall not reap the aftergrowth of your harvest or gather the grapes of
your untrimmed vines; it shall be a year of complete rest for the
land. (Vayikra 25:2ff)