The phrase "were mid-air" indicates a state of being suspended in the air. Antonyms for this phrase would be words that describe being firmly on the ground, such as "landed," "grounded," and "stationary." Other antonyms could include words that describe a downward movement, such as "descending," "falling," or "crashing." Additionally, words that indicate a lack of movement or action could also be antonyms, such as "still," "inactive," or "motionless." In summary, antonyms for "were mid-air" would include words that describe being on the ground, moving downward, or lacking any movement.