Abstract: Aircraft passenger seat frames (60, 62, 220, 222 and 224) having legs (54, 56, 210, 212) fixed in place in the aircraft and with the seat frames. Each seat frame has generally horizontal supporting members (66, 68, 74, 76) having their opposite ends secured in seat end webs (70, 72, 78, 80). Tubes (84, 86) are associated with each of the seat end webs of the plurality of seat frames in a supporting relationship, the legs (54, 56) being connected to the tubes to support the seat frames. The tubes have a tube-in-tube slip joint (88, 90) at least at one outside end of the one seat frame on which the seat can be moved toward or away from an adjacent seat frame to change the fare class size of the set frames.