Olympic-class ocean liner so, the "Olympic"-class ships were built to surpass rival Cunard's largest ships, "Lusitania" and "Mauretania", in size and luxury. "Olympic", along with "Titanic" and the soon to be built "Britannic", were intended to be the largest and most luxurious ships to operate on the North Atlantic, but not the fastest, as the White Star Line had already switched from high speed to size and luxury. The three vessels were designed by Thomas Andrews and Alexander Carlisle. Construction of "Olympic" started in December 1908 and "Titanic" in March 1909. The two ships were built side by side. The construction of "Britannic"
Sister ship an . The most famous sister ships were the White Star Line's , and . As with some other liners, the sisters worked as running mates. Other sister ships include the Royal Caribbean International's and . "Half-sister" refers to a ship of the same class but with some significant differences. One example of half-sisters are the First World War-era British s where the first two ships had four guns, but the last ship, , had two guns instead. Another example is the American s of the Second World War that came in "long-hull" and "short-hull" versions. Notable airships include the