Antonyms for the phrase "became airborne" would refer to actions that imply the opposite of flying or taking off. These can include terms such as "laid down," "grounded," or "landed." Other antonyms might include "refused to take off," "remained stationary," or "stayed grounded." Depending on the context of the phrase, other antonyms could include actions like "stopped in mid-air," "crashed down," or "fell to the ground." In any case, antonyms for "became airborne" typically suggest a lack of movement or an inability to fly, as opposed to the upward motion implied by the phrase.