A seat, especially an aircraft passenger seat, has seat components such as a seat part, a seat back (3), and a shell body (5). The shell body forms at least a partially rear enclosure (9) of the seat part and the seat back (3). With an adjusting mechanism, the seat part and the seat back (3) can be adjusted in position relative to one another and relative to the rear enclosure (9). The distance between the rear enclosure and the seat back (3) is variable. A cover assembly (31, 45) bridges a distance formed by the variable distance between the seat back (3) and enclosure (9) between formed gaps.