Project 10073 Record Card and Air Intelligence Information Report — Thule Air Base, Greenland, April 1952

This document consists of a Project 10073 record card and an associated Air Intelligence Information Report (IR-13-52) regarding a sighting at Thule Air Base, Greenland, on April 25, 1952. At approximately 0100 local time, a Lieutenant and a civilian employee from the Arctic Rescue unit observed a vapor trail at an altitude estimated to be above 30,000 feet. The weather conditions at the time were reported as clear with unlimited visibility. The witnesses attempted to identify the source of the vapor trail using binoculars but were unable to distinguish any aircraft at the originating point. The report notes that an aircraft, number 5555, piloted by Captain Edward Nancy Dahlborg, was in the area at the time. However, Captain Dahlborg stated that his aircraft was at an altitude of 4,000 feet, which he deemed too low to produce the observed vapor trail. The report mentions that similar incidents had allegedly occurred at the station in January 1952 but were not reported at the time. The evaluation of the incident was classified as C-3, and an investigation was requested. The document is marked as unclassified and includes instructions for downgrading and declassification under DOD Directive 5200.10.