This memorandum summarizes a Central Intelligence Agency (CIA) debriefing of a group of four individuals who reported observing a “flying saucer” or “unconventional aircraft” in 1955. The group, which included U.S. Senator Richard Russell, a U.S. military service member, and two U.S. Government officials, reported observing a luminescent “greenish-yellow” phenomenon, as seen from aboard a train while traveling within the Soviet Union, in present-day Azerbaijan, between Baku and Tiflis (Tbilisi, Georgia). The document concludes by stating that the observation can “probably be explained as steep climbing aircraft or missiles,” and that “the evidence does not appear sufficiently firm to warrant the conclusion that the Soviets have developed […] a radically new type of aircraft.” The document “CIA-UAP-D021” contains a contemporary analysis of the incident.