The antonyms for the phrase "becomes airborne" are "remains grounded" or "stays on the ground." When an object or living being becomes airborne, it means that it has lifted off the ground and is now suspended in the air. This term is commonly used in reference to birds, planes, and other flying objects. On the other hand, when something remains grounded, it means that it is still on the ground and has not taken flight. This can also refer to emotions or events that are not able to take off or escalate.