The kitchens in railway dining cars have presented special challenges: space is limited, and, personnel must be able to serve a great number of meals quickly. Especially in the early history of railways, this required flawless organization of processes; in modern times, the microwave oven and prepared meals have made this task much easier. Kitchens aboard ships, aircraft and sometimes railcars are often referred to as galleys. On yachts, galleys are often cramped, with one or two burners fueled by an LP gas bottle. Kitchens on cruise ships or large warships, by contrast, are comparable in every respect with restaurants or canteen kitchens.