RMS Olympic Ismay had previously planned to build a ship named "Olympic" as a sister ship to . The senior Ismay died in 1899 and the order for the ship was cancelled. Construction of "Olympic" began three months before "Titanic" to ease pressures on the shipyard. Several years would pass before "Britannic" would be launched. In order to accommodate the construction of the class, Harland and Wolff upgraded their facility in Belfast; the most dramatic change was the combining of three slipways into two larger ones. "Olympic" and "Titanic" were constructed side by side. "Olympic"s keel was laid on 16 December 1908
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