There is no cost associated with waitlisting. You will be asked for a credit card but not charged unless you actually travel. While we can never guarantee a seat if you are waitlisted, your chances are 0% if you do not which is why we always encourage passengers to waitlist. If we have enough passengers waitlisted we do have the option of adding extra flights. If a seat opens up we will confirm with you whether or not you still want the seat, you are given the option to say yes or no without being penalized.