A robot system for carrying out a plurality of operations during assembly or maintenance of an aircraft or spacecraft, the robot system comprising: - a first robot adapted to be positioned in proximity of a fuselage of an aircraft or spacecraft and comprising - a base portion, - a movable robot arm connected at one end to the base portion and having at an opposite end a first coupling portion, and - a first control means adapted to control the robot arm, and - a plurality of second robots, each being smaller than the first robot and comprising - movement means allowing the respective second robot to be supported on a ground surface and allowing translational movement of the second robot along the ground surface and rotary motion about an axis perpendicular to the ground surface, - a drive portion operable to drive the movement means to effect at least the translational movement of the respective second robot, - a tool portion comprising a tool adapted to carry out a specific operation of the plurality of operations, and - a second coupling portion adapted to be selectively and releasably coupled with the first coupling portion in a predetermined positional relationship, and - a second control means adapted to control the respective second robot, wherein for each operation of the plurality of operations the plurality of second robots includes at least one second robot the tool of which is adapted to carry out the respective operation, and wherein the first and second control means (17, 18) are adapted to control - the drive portion of one of the second robots and the robot arm to couple the first coupling portion and the respective second coupling portion in the predetermined positional relationship, - subsequently the robot arm to move the tool portion together with the second robot held by the robot arm to a selected location at which the specific operation, for which the tool portion of the respective second robot is adapted, is to be carried out, and - then the second robot to carry out the specific operation at the selected location. - a first robot adapted to be positioned in proximity of a fuselage of an aircraft or spacecraft and comprising - a base portion, - a movable robot arm connected at one end to the base portion and having at an opposite end a first coupling portion, and - a first control means adapted to control the robot arm, and - a base portion, - a movable robot arm connected at one end to the base portion and having at an opposite end a first coupling portion, and - a first control means adapted to control the robot arm, and - a plurality of second robots, each being smaller than the first robot and comprising - movement means allowing the respective second robot to be supported on a ground surface and allowing translational movement of the second robot along the ground surface and rotary motion about an axis perpendicular to the ground surface, - a drive portion operable to drive the movement means to effect at least the translational movement of the respective second robot, - a tool portion comprising a tool adapted to carry out a specific operation of the plurality of operations, and - a second coupling portion adapted to be selectively and releasably coupled with the first coupling portion in a predetermined positional relationship, and - a second control means adapted to control the respective second robot, wherein for each operation of the plurality of operations the plurality of second robots includes at least one second robot the tool of which is adapted to carry out the respective operation, and wherein the first and second control means (17, 18) are adapted to control - movement means allowing the respective second robot to be supported on a ground surface and allowing translational movement of the second robot along the ground surface and rotary motion about an axis perpendicular to the ground surface, - a drive portion operable to drive the movement means to effect at least the translational movement of the respective second robot, - a tool portion comprising a tool adapted to carry out a specific operation of the plurality of operations, and - a second coupling portion adapted to be selectively and releasably coupled with the first coupling portion in a predetermined positional relationship, and - a second control means adapted to control the respective second robot, - the drive portion of one of the second robots and the robot arm to couple the first coupling portion and the respective second coupling portion in the predetermined positional relationship, - subsequently the robot arm to move the tool portion together with the second robot held by the robot arm to a selected location at which the specific operation, for which the tool portion of the respective second robot is adapted, is to be carried out, and - then the second robot to carry out the specific operation at the selected location.