For airports and aviation facilities, fire pumps must meet high reliability and performance standards due to the large spaces and high-risk environments. Bothdiesel engine fire pumpsandelectric fire pumpsare used, often UL listed and NFPA 20 compliant. They may be part of a large, distributed system with jockey pumps for pressure maintenance. Diesel pumps are preferred for backup or as the primary source when electricity supply reliability is an issue.