A Standby Flight refers to a flight option that allows passengers to travel on their desired flight without canceling the original booking. Travelers may choose the Standby Flight option if they want to take an earlier or later flight than originally booked due to an emergency. Further, Standby status is only given when the available flight is flying to the same destination and on the same date. To learn more about this, contact the customer service or airline, or check out the blog linked here.