The phrase "are in mid-air" implies some kind of suspended animation or movement. Antonyms for this phrase could include "are grounded," "are stationary," or "are at rest." The opposite of being in motion is to be still, so these antonyms suggest a state of being settled or stationary. Additionally, the phrase "are in mid-air" can also suggest uncertainty or indecisiveness, so antonyms might include "are decisive" or "are resolute." These suggest a state of being sure and confident in one's choices, as opposed to being mired in doubt or uncertainty.