A union flying squad is an unofficial group of autonomous workers (usually members of a single trade union) who carry out actions for the benefit of their labor struggle. Squads are a form of affinity groups and may be formed by union members who feel that the union bureaucracy is not working satisfactorily in their interest or for the interest of a unified labor movement. In the case of some democratic and militant unions like the Canadian Auto Workers, flying squads were formed with the support and encouragement of the official union structures. They may be called in to bulk up picket lines, to discourage bosses from using strikebreakers. The first reference to a flying squad may originate with a remark by Friedrich Engels during an uprising in Paris during the 19th century.