I suspect that a lot of UFO activity in the latter part of the 1940s in the United States had more to do with classified, military experimentation than it did with aliens. There is, however, no doubt that there was a significant number of UFO reports from that period which are not so easy to dismiss. In many such cases, UFOs intruded upon sensitive military/government airspace in the United States. In the latter part of the 1940s – and particularly so in 1948 – a curious phenomenon was repeatedly seen in the skies over New Mexico. They were strange, glowing balls of green light that seemed to take a disturbing amount of interest in the many defense, atomic, and military establishments that existed in the state at the time. A program designed to investigate the reports, which was given the name of Project Twinkle, was soon put into place.
Consider the following, written by Lt. Col. Doyle Rees of the Air Force’s Office of Special Investigations (AFOSI) at Kirtland Air Force Base, New Mexico, on 25 May 1950. It was for the specific attention of Brigadier General Joseph F. Carroll, Director of Special Investigations, USAF:
"In a liaison meeting with other military and government intelligence and investigative agencies in December 1948, it was determined that the frequency of unexplained aerial phenomena in the New Mexico area was such that an organized plan of reporting these observations should be undertaken. The organization and physical location of units of this District were most suitable for collecting these data, therefore, since December 1948, this District has assumed the responsibility for collecting and reporting basic information with respect to aerial phenomena occurring in this general area."
And a large body of that so-called “basic information” was profound, to say the very least. A Federal Bureau of Investigation (FBI) memorandum dated 31 January 1949 and titled Protection of Vital Installations, reveals the following: "During the past two months various sightings of unexplained phenomena have been reported in the vicinity of the Atomic Energy Commission Installation at Los Alamos, New Mexico, where these phenomena now appear to be concentrated [emphasis mine]. During December 1948 on the 5th, 6th, 7th, 8th, 11th, 13th, 14th, 20th, and 28th sightings of unexplained aerial phenomena were made near Los Alamos by Special Agents of the Office of Special Investigations; Airline Pilots; Military Pilots; Los Alamos Security Inspectors; and private citizens. On January 6, 1949, another similar object was sighted in the same area." Moving on...
It's intriguing to note that the atomic research facility at Oak Ridge, Tennessee was also a magnet for countless close encounters with UFOs - in the late 1940s and the early 1950s. Consider, for example, the following official report generated on 2 March 1950 by the Atomic Energy Commission (AEC):
"There is a radar station near Knoxville which has been in operation about 3 weeks. This radar station is being operated by station WROL of Knoxville. On 1 March at 2135 hours the station picked up an object 340 degrees and 18 miles from Knoxville, altitude 40,000 feet. Direction and distance put the object directly over [emphasis mine] Oak Ridge. AEC Security Division Chief at Oak Ridge checked with Smyrna Air Base, Nashville which reported it had no flight plan for any plane in that vicinity and altitude. On 2 March at 1105 station picked up object at 335 degrees and 18 miles from Knoxville, altitude 40,000 feet. AEC Security Division Chief checked with Smyrna Air Base with negative results."
On the following day, 3 March, 1950, a further report surfaced: "At 2130 hours on 2nd March, radar station picked up two objects 310 degrees, altitude 80,000 feet, approximately 18 miles from Knoxville in general direction of Oak Ridge, moving in circular motion but in opposite directions." And Oak Ridge continued to be a target for the mysterious intruders. An FBI teletype of 13 October 1950 refers to the detection of a veritable squadron of unknown objects tracked over the Oak Ridge installation at 11.25 p.m. on 12 October: "USAF radar installation at Knoxville picked up indications of eleven objects and perhaps more traveling across controlled area of Atomic Energy installation at Oak Ridge [emphasis mine]…operators are experienced reliable personnel and radar set is in perfect operating condition."
Perhaps most significant of all, is the following FBI document that offers the significant thoughts and conclusions of Oak Ridge personnel with respect to the UFO invasions in sensitive airspace:
"The opinions of the Security Division, AEC Oak Ridge; Security Branch, NEPA [Nuclear Energy for Propulsion of Aircraft project] Division, Oak Ridge; AEC Security Patrol, Oak Ridge; FBI Knoxville; Air Force Radar and Fighter Squadrons, Knoxville; and the OSI, Konxville, Tennessee, fail to evolve an adequate explanation for OBJECTS SIGHTED OVER OAK RIDGE, TENNESSEE; however, the possibilities of practical jokers, mass hysteria, balloons of any description, flights of birds, falling leaves, insect swarms, peculiar weather conditions, reflections, flying kites, objects thrown from the ground, windblown objects, insanity, and many other natural happenings have been rejected because of the simultaneous witnessing of the objects with the reported radar sightings; because of the reliability of the witnesses; because of the detailed, similar description of the objects seen by different persons…"
Note that in the above-paragraph the words "objects sighted over Oak Ridge" were all typed in capital letters, further demonstrating the concern over such cases.
Not exactly outright invasions, but pretty damn close.