Load factor is a metric used primarily in the transportation industry. A company's load factor is defined as percentage of their available seats that are filled.
Companies can determine a minimum load factor they need to meet in order to break even financially. That is, once a company meets a certain load factor the revenues from doing so will cover the costs of providing their seat capacity. If they are below this break-even load factor the company will be spending more than they are earning and will lose money.