A seat back tray table (10; 30), comprising: an arm assembly attachable to a seat having a seat back, and moveable between a stowed position and a deployed, use position, the arm assembly comprising a pair of laterally-opposed arms (12, 14; 32, 34) connected by a pivotally-mounted stabilizing cross bar (16; 36); a first table segment (18; 38) carried by the arm assembly and moveable with the arm assembly between a stowed position within or proximate a stowage area of the seat back and a deployed position aft of the stowage area; a second table segment (22; 40) carried by the first table segment (18; 38) and moveable between a stored position within or proximate to the stowage area of the seat back and an extended position laterally-extended from the first table segment to increase the total surface area of the tray table (10; 30) when the first table segment (18; 38) is in its deployed position; and wherein the width of the tray table (10; 30) in its fully stowed position is about one-half of the width of the seat back and in its fully deployed position is substantially the entire width of the seat back; and the seat back tray table further including a pocket (20; 42) positioned on a bottom side of the first table segment (18; 38), wherein the second table segment in its stored position is telescoped into the pocket in the first table segment and adapted to be translated laterally-outwardly from the pocket into the deployed, use position; or wherein the second table segment is mounted for pivotal movement on a vertical axis and in its stored position is rotated into the pocket in the first table segment and adapted to be rotated laterally on the vertical axis outwardly from the pocket into the deployed, use position. an arm assembly attachable to a seat having a seat back, and moveable between a stowed position and a deployed, use position, the arm assembly comprising a pair of laterally-opposed arms (12, 14; 32, 34) connected by a pivotally-mounted stabilizing cross bar (16; 36); a first table segment (18; 38) carried by the arm assembly and moveable with the arm assembly between a stowed position within or proximate a stowage area of the seat back and a deployed position aft of the stowage area; a second table segment (22; 40) carried by the first table segment (18; 38) and moveable between a stored position within or proximate to the stowage area of the seat back and an extended position laterally-extended from the first table segment to increase the total surface area of the tray table (10; 30) when the first table segment (18; 38) is in its deployed position; and wherein the width of the tray table (10; 30) in its fully stowed position is about one-half of the width of the seat back and in its fully deployed position is substantially the entire width of the seat back; and the seat back tray table further including a pocket (20; 42) positioned on a bottom side of the first table segment (18; 38), wherein the second table segment in its stored position is telescoped into the pocket in the first table segment and adapted to be translated laterally-outwardly from the pocket into the deployed, use position; or wherein the second table segment is mounted for pivotal movement on a vertical axis and in its stored position is rotated into the pocket in the first table segment and adapted to be rotated laterally on the vertical axis outwardly from the pocket into the deployed, use position.