A fuselage comprising: a plurality of frames (202A-E), wherein each frame (202A-E) comprises a lateral floor beam (204A-E); and a plurality of seat rows (206A-D) spaced apart according to a seat pitch, wherein each seat row of the plurality of seat rows (206A-D) comprises: a load-bearing structural base with a plurality of legs (210, 212) attached to a proximal lateral floor beam and a distal lateral floor beam; a seat or bank of seats attached to the load-bearing structural base, wherein the seat or bank of seats comprises at least one seat bottom and at least one seat back; and an interface between (i) the load-bearing structural base and (ii) the seat or bank of seats to allow for attachment and detachment of the seat or bank of seats relative to the load-bearing structural base; wherein: the plurality of legs (210, 212) are attached to the proximal lateral floor beam and the distal lateral floor beam without attachment to a seat track; the load-bearing structural base is attached to the proximal lateral floor beam and the distal lateral floor beam through a plurality of connection fittings (350, 352, 380, 382, 390), wherein each connection fitting (350, 352, 380, 382, 390) comprises a first portion (354, 358) connected to one of the plurality of legs (210, 212) and a second portion (356, 360) connected to the proximal lateral floor beam or distal lateral floor beam; the plurality of legs (210, 212) comprise (i) a front leg attached to the proximal lateral floor beam and (ii) a rear leg attached to the distal lateral floor beam; the plurality of seat rows (206A-D) comprise a first seat row and a second seat row; the front leg of the load-bearing structural base of the second seat row is attached to one of the plurality of connection fittings; and wherein the rear leg of the load-bearing structural base of the first row is attached to the same one of the plurality of connection fittings. a plurality of frames (202A-E), wherein each frame (202A-E) comprises a lateral floor beam (204A-E); and a plurality of seat rows (206A-D) spaced apart according to a seat pitch, wherein each seat row of the plurality of seat rows (206A-D) comprises: a load-bearing structural base with a plurality of legs (210, 212) attached to a proximal lateral floor beam and a distal lateral floor beam; a seat or bank of seats attached to the load-bearing structural base, wherein the seat or bank of seats comprises at least one seat bottom and at least one seat back; and an interface between (i) the load-bearing structural base and (ii) the seat or bank of seats to allow for attachment and detachment of the seat or bank of seats relative to the load-bearing structural base; wherein: the plurality of legs (210, 212) are attached to the proximal lateral floor beam and the distal lateral floor beam without attachment to a seat track; the load-bearing structural base is attached to the proximal lateral floor beam and the distal lateral floor beam through a plurality of connection fittings (350, 352, 380, 382, 390), wherein each connection fitting (350, 352, 380, 382, 390) comprises a first portion (354, 358) connected to one of the plurality of legs (210, 212) and a second portion (356, 360) connected to the proximal lateral floor beam or distal lateral floor beam; the plurality of legs (210, 212) comprise (i) a front leg attached to the proximal lateral floor beam and (ii) a rear leg attached to the distal lateral floor beam; the plurality of seat rows (206A-D) comprise a first seat row and a second seat row; the front leg of the load-bearing structural base of the second seat row is attached to one of the plurality of connection fittings; and wherein the rear leg of the load-bearing structural base of the first row is attached to the same one of the plurality of connection fittings. the plurality of legs (210, 212) are attached to the proximal lateral floor beam and the distal lateral floor beam without attachment to a seat track; the load-bearing structural base is attached to the proximal lateral floor beam and the distal lateral floor beam through a plurality of connection fittings (350, 352, 380, 382, 390), wherein each connection fitting (350, 352, 380, 382, 390) comprises a first portion (354, 358) connected to one of the plurality of legs (210, 212) and a second portion (356, 360) connected to the proximal lateral floor beam or distal lateral floor beam; the plurality of legs (210, 212) comprise (i) a front leg attached to the proximal lateral floor beam and (ii) a rear leg attached to the distal lateral floor beam; the plurality of seat rows (206A-D) comprise a first seat row and a second seat row; the front leg of the load-bearing structural base of the second seat row is attached to one of the plurality of connection fittings; and wherein the rear leg of the load-bearing structural base of the first row is attached to the same one of the plurality of connection fittings.