An assembly including a plurality of seats arranged in a row along a longitudinal axis X, each seat including an armchair and a lateral box arranged laterally to said armchair, in which assembly: each armchair has a front side oriented substantially in the same direction; the armchairs, on the one hand, and the lateral boxes, on the other hand, are arranged in a staggered manner in two rows parallel to the longitudinal axis X, each seat including a covering shell determining a rear surface in a rear zone of the armchair and determining a front surface in a front zone of the lateral box, a space between a rear surface of a front seat and a front surface of a rear seat, located immediately behind said front seat in the assembly, forming a passage for an occupant of said rear seat, characterized in that : - in a section formed in a vertical plane in which there is a minimum width Lmin of the passage , the rear surface and the front surface have convex profiles facing each other, a width L(hz) of said passage in said vertical plane increasing continuously in the direction of the heights hz, above a reference cabin floor , decreasing from a height hzmin of the minimum width Lmin, at least up to the vicinity of the floor , and said width L(hz) increasing continuously in the direction of the increasing heights hz from said height hzmin of the minimum width Lmin, such that the width L(hz) has a single point of change in the direction of variation (hzmin, Lmin); - the rear surface has a convex shape in sections along horizontal planes, giving, combined with the convex profiles in a section along a vertical plane, to said rear surface a pseudo-ellipsoidal cap shape; - the front surface in a front zone of the lateral box has a substantially straight shape in sections along horizontal planes, giving to said front surface a partial cylinder shape with substantially horizontal axis and generators; - the rear surface of the front seat and the front surface of the rear seat giving the passage a convergent-divergent shape with a neck of width Lmin guiding a user of the seat. - in a section formed in a vertical plane in which there is a minimum width Lmin of the passage , the rear surface and the front surface have convex profiles facing each other, a width L(hz) of said passage in said vertical plane increasing continuously in the direction of the heights hz, above a reference cabin floor , decreasing from a height hzmin of the minimum width Lmin, at least up to the vicinity of the floor , and said width L(hz) increasing continuously in the direction of the increasing heights hz from said height hzmin of the minimum width Lmin, such that the width L(hz) has a single point of change in the direction of variation (hzmin, Lmin); - the rear surface has a convex shape in sections along horizontal planes, giving, combined with the convex profiles in a section along a vertical plane, to said rear surface a pseudo-ellipsoidal cap shape; - the front surface in a front zone of the lateral box has a substantially straight shape in sections along horizontal planes, giving to said front surface a partial cylinder shape with substantially horizontal axis and generators; - the rear surface of the front seat and the front surface of the rear seat giving the passage a convergent-divergent shape with a neck of width Lmin guiding a user of the seat. <EOS>