The B-52 Stratofortress was a strategic heavy bomber in service with the USAF in the latter half of the 20th century.
A picture of one of these aircrafts was seen in the Statistical services division, a room located in the headquarters of the 498th Airbase Group in Omaha, Nebraska. (TOS: "Tomorrow is Yesterday")
The color scheme of this bomber identified it as being the "mother ship" of an X-15.