The function of the flying buttress is to take the thrust from a central vault and carry it over the lateral aisle to the external buttresses. Flying buttresses also resist lateral loads such as wind and seismic loads. When there is an additional upper tier, its main function is to carry these lateral loads. The structural behavior of flying buttresses has been studied by several authors since the 19th century with different approaches. An accurate survey of the cathedral of Mallorca has been used to study these elements. The flying buttresses in the cathedral of Mallorca, with ca. 9m span and around 30 tons weight, are probably the biggest in Gothic architecture. Their position approximately 30m above ground makes them very sensitive to the leaning of the buttresses. First, an overview of the structural behavior of flying buttresses will be provided, within the theoretical framework of limit analysis. Then, the general equilibrium, deformations and crack patterns of the flying buttresses in the cathedral of Mallorca will be analyzed. The local problems, such as the sliding of the head of the flyers, and the different solutions that have been adopted trough history will be studied.