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  1. 1 UFO is short for “unidentified flying object”, a term that came from the US Air Force. The National Archives
  2. 2 To the military, a UFO means something in the sky that can be seen but not recognised. It does not mean something from another world. The National Archives
  3. 3 Britannica defines a UFO as any object or light in the sky that the person watching can’t readily identify. Britannica
  4. 4 Some branches of the UK Ministry of Defence prefer the term UAP, for “unidentified aerial phenomena”. The National Archives
  5. 5 The US Defense Department calls UAP a new term for what used to be called unidentified flying objects. US Defense Dept, 2024
  6. 6 When NASA’s UAP study began, the US Congress defined UAP as “unidentified aerial phenomena”. During the study, the term was changed to “unidentified anomalous phenomena”. NASA UAP study
  7. 7 NASA describes UAP as observations of events in the sky that can’t be identified as aircraft or known natural phenomena. NASA Science
  8. 8 AARO, the US government’s UAP office, says many cases are labelled “unidentified” simply because the sensors didn’t collect enough information to say what they were. AARO FAQ
  9. 9 In the UK, official reporting and recording of UFO sightings began in the early 1950s. The National Archives
  10. 10 Until 1967 the Ministry of Defence destroyed its UFO files every five years, so many early records are lost. The National Archives
  11. 11 Since 1970, most surviving MoD UFO files have been reviewed for release at The National Archives, because so many people are interested. The National Archives
  12. 12 On 24 June 1947, private pilot Kenneth Arnold was flying past Mount Rainier in Washington State, USA. Smithsonian Air and Space
  13. 13 Arnold was an experienced pilot with 4,000 flying hours and a member of an Idaho search and rescue unit. Smithsonian Air and Space
  14. 14 He was making a detour to look for a crashed US Marine Corps transport plane, hoping to claim a $5,000 reward. Smithsonian Air and Space
  15. 15 Shortly before 3 p.m. he saw a bright flash and at first assumed it was sunlight glinting off a military plane. Smithsonian Air and Space
  16. 16 He said the flashes came from nine shiny objects flying in a formation about five miles long, each about 100 feet across with no tail he could see. Smithsonian Air and Space
  17. 17 He said they moved like a saucer skipping on water. The National Archives
  18. 18 He timed them flying from Mount Rainier to Mount Adams and worked out a speed of about 1,200 mph; some accounts say 1,700 mph. Smithsonian Air and Space
  19. 19 Britannica says Arnold estimated their speed at several thousand miles per hour, and calls the objects crescent-shaped. Britannica
  20. 20 A newspaper report then wrongly said the objects were saucer-shaped, which is how we got the phrase “flying saucer”. Britannica
  21. 21 Arnold strongly denied first calling them “flying saucers”, though stories at the time say he used the words saucer, disc and pie-pan. Smithsonian Air and Space
  22. 22 A reporter’s story for the Associated Press described “nine bright saucer-like objects”, and by that afternoon “flying saucers” had spread across the United States. Smithsonian Air and Space
  23. 23 In a report he sent to the US Air Force that July, Arnold drew a shape rather like the heel of a shoe, not a round saucer. Smithsonian Air and Space
  24. 24 The National Archives calls Arnold’s sighting the first report of “flying saucers”. The National Archives
  25. 25 The Smithsonian says nobody will ever know exactly what Arnold saw, and that it remains unexplained. Smithsonian Air and Space
  26. 26 The Smithsonian’s air and space museum urges everyone looking at the sky to use critical thinking about whatever they see. Smithsonian Air and Space
  27. 27 Arnold’s sighting kicked off a craze, and hundreds of UFO sightings began pouring in. Smithsonian, Roswell
  28. 28 The Roswell incident was the crash and recovery of a US Army Air Forces high-altitude balloon near Roswell, New Mexico, in 1947, which became the centre of a conspiracy theory about aliens. Britannica, Roswell
  29. 29 A rancher, W.W. “Mac” Brazel, found unusual debris on a ranch near Roswell. Britannica, Roswell
  30. 30 The debris included tinfoil, rubber strips and sticks. Britannica, Roswell
  31. 31 Brazel took the find to the sheriff, who contacted the local military airfield. Britannica, Roswell
  32. 32 The airfield put out a press release saying a “flying disc” had been recovered. Britannica, Roswell
  33. 33 On 8 July 1947 the Roswell Daily Record’s headline read “RAAF Captures Flying Saucer On Ranch in Roswell Region”. Britannica, Roswell
  34. 34 Almost at once, the military said the “saucer” was really a weather balloon carrying a radar target, a kind of box kite made of foil-covered paper on a balsa wood frame. Britannica, Roswell
  35. 35 Brazel himself told a newspaper he didn’t believe the debris came from a weather balloon. Britannica, Roswell
  36. 36 The story faded until a 1980 book, The Roswell Incident, called the weather balloon explanation a cover story. Britannica, Roswell
  37. 37 Documents that surfaced in 1984 about a secret group called Majestic 12 were later found to be fake. Britannica, Roswell
  38. 38 A 1995 “alien autopsy” film was later called a fraud by its own director. Britannica, Roswell
  39. 39 Roswell now has an International UFO Museum and Research Center (opened 1992) and has held a UFO festival every year since 1996. Britannica, Roswell
  40. 40 In 1994, after a member of Congress asked the Government Accountability Office to look into it, the US Air Force searched its records on Roswell. US Air Force
  41. 41 The 1994 Air Force report concluded that the debris came from a balloon-borne research project code-named Mogul. US Air Force
  42. 42 Project Mogul was a top-secret attempt to detect Soviet nuclear bomb tests. Britannica, Roswell
  43. 43 Its balloons carried instruments high into the atmosphere to pick up the sound waves from an atomic bomb test. Smithsonian, Roswell
  44. 44 So the book was right about one thing: the weather balloon story was wrong. It was a spy balloon. Britannica, Roswell
  45. 45 The Air Force found nothing to show the Roswell incident was a UFO event, and no sign of a government cover-up. US National Archives
  46. 46 No records even hinted at the recovery of alien bodies or materials from space. US National Archives
  47. 47 A 1997 Air Force report said the “aliens” people described were probably human-shaped test dummies carried up by high-altitude research balloons. US Air Force
  48. 48 It said events that happened over many years had been merged in people’s memories into two or three days in July 1947. US Air Force
  49. 49 For many UFO enthusiasts, these explanations were simply more cover-up. Britannica, Roswell
  50. 50 The Government Accountability Office published its own report on its search for Roswell records in July 1995. GAO
  51. 51 Area 51 in Nevada, another favourite of alien stories, has only one confirmed use: testing aircraft. Britannica, Roswell
  52. 52 As reports grew, the US Air Force began an investigation called Project Sign in 1948. Britannica
  53. 53 Its investigators first thought UFOs were most likely advanced Soviet aircraft, though some suggested spacecraft from other worlds. Britannica
  54. 54 Sign became Project Grudge, which in 1952 was replaced by Project Blue Book, the longest-running official UFO inquiry. Britannica
  55. 55 Project Blue Book began in March 1952 and took reports from the public as well as the military. Britannica, Blue Book
  56. 56 It was based at Wright-Patterson Air Force Base, near Dayton, Ohio. Britannica, Blue Book
  57. 57 It was named after the blue exam booklets used in American colleges, to suggest a careful, methodical approach. Britannica, Blue Book
  58. 58 Its staff created a standard questionnaire for sighting reports. Britannica, Blue Book
  59. 59 From 1947 to 1969, 12,618 sightings were reported to Project Blue Book (counting the earlier projects too). US National Archives
  60. 60 Britannica’s UFO article gives the same 12,618 total but dates it from 1952 to 1969. Britannica
  61. 61 Of those, 701 stayed “unidentified”. US National Archives
  62. 62 The unidentified cases included ones where there wasn’t enough information to match a known cause. Britannica
  63. 63 Most sightings got ordinary explanations; the biggest single group was mistaken military or civilian aircraft. Britannica, Blue Book
  64. 64 A CIA history declassified in 2014 says U-2 and later OXCART spy-plane flights accounted for more than half of all UFO reports in the late 1950s and most of the 1960s. Britannica
  65. 65 1952 had 303 unexplained sightings, many of them over Washington, D.C., that July. Most years had about a dozen. Britannica, Blue Book
  66. 66 The 1952 Washington sightings, on radar and by eye, were put down to temperature inversions in the air over the city, though not everyone was convinced. Britannica
  67. 67 In 1953 a panel of scientists led by physicist H.P. Robertson met for three days and reviewed films and photographs of UFOs. Britannica
  68. 68 The panel concluded that 90 per cent of sightings could easily be put down to things like bright planets and stars, meteors, aircraft, balloons, birds and searchlights, and that there was no evidence for alien visitors. Britannica
  69. 69 Parts of the panel’s report stayed secret until 1979, which helped fuel suspicions of a cover-up. Britannica
  70. 70 A University of Colorado study led by physicist Edward Condon looked in detail at 59 sightings and found no evidence of anything but ordinary phenomena. Britannica
  71. 71 Project Blue Book was closed on 17 December 1969. Britannica, Blue Book
  72. 72 Its conclusions: no UFO was ever a threat to US security, and there was no evidence that the “unidentified” sightings were beyond known science or were vehicles from space. US National Archives
  73. 73 No physical evidence of anything from another world was collected during the project. Britannica, Blue Book
  74. 74 Astronomer J. Allen Hynek, the project’s lead scientist throughout, was privately critical of its lack of rigour and its emphasis on debunking. Britannica, Blue Book
  75. 75 Hynek later concluded that a small fraction of the most reliable reports pointed to visitors from space, and founded the Center for UFO Studies. Britannica
  76. 76 Blue Book’s declassified records have been at the US National Archives in Washington, D.C., since 1976, open to the public. Britannica, Blue Book
  77. 77 Today you read them on 94 rolls of microfilm in the National Archives’ reading room. US National Archives
  78. 78 The Rendlesham Forest sightings happened over two nights in late December 1980, near RAF Woodbridge in Suffolk, an airbase lent to the US Air Force. National Archives briefing
  79. 79 The National Archives calls it Britain’s best-known UFO incident. National Archives, 2009 files
  80. 80 It is often called “Britain’s Roswell”. National Archives briefing
  81. 81 Mysterious lights were seen to come down in the forest, and airmen who went to look reported lights they couldn’t identify moving through the trees. National Archives briefing
  82. 82 The next day, marks were allegedly found on the ground and on trees where the men said the UFO had landed. National Archives briefing
  83. 83 Two nights later the deputy base commander, Lt Col Charles Halt, took a team into the woods, saw several unidentified lights and recorded a live tape. National Archives briefing
  84. 84 In January 1981 Halt sent the Ministry of Defence an official report titled “Unexplained Lights”. National Archives briefing
  85. 85 The US airmen claimed a UFO had landed, leaving markings on the ground and radiation. National Archives, 2009 files
  86. 86 The Rendlesham papers were among the first UFO files the MoD released to the public, in 2001. National Archives briefing
  87. 87 The story became famous in 1983, when the News of the World published it. National Archives briefing
  88. 88 In 2001 the government told the House of Lords that Halt’s memo was the only US Air Force material the MoD held on the incident. Hansard
  89. 89 MoD records from the time show no evidence of unusual radar returns. Hansard
  90. 90 Sceptical investigators point out that a bright fireball burned up over southern England at about 3 a.m. on 26 December 1980, the time of the first sighting. Skeptical Inquirer, 2015
  91. 91 They say the flashing light in the trees was the Orford Ness lighthouse, which stood in the direction the airmen were looking and flashed every five seconds, just like the “UFO”. Skeptical Inquirer, 2014
  92. 92 Local police soon worked out the lighthouse explanation, according to the same sceptical review. Skeptical Inquirer, 2014
  93. 93 Local police and a forester identified the ground marks as rabbit scrapings and the tree marks as cuts made by foresters. Skeptical Inquirer, 2015
  94. 94 Halt’s radiation readings showed only background levels, says the sceptics’ account. Skeptical Inquirer, 2015
  95. 95 The star-like objects in Halt’s memo were probably real stars: Sirius, Vega and Deneb. Skeptical Inquirer, 2014
  96. 96 In the sceptics’ summary, the whole case comes down to three ordinary night lights seen together: a fireball, a lighthouse and some stars. Skeptical Inquirer, 2015
  97. 97 Nick Pope, who once assessed UFO reports part-time for the MoD, wrote a book with two of the airmen calling it the best-documented and most compelling UFO incident ever. Skeptical Inquirer, 2014
  98. 98 Sceptics note the story has grown with each retelling, with new claims added years later. Skeptical Inquirer, 2015
  99. 99 Today Forestry England runs a UFO trail in Rendlesham Forest. Forestry England
  100. 100 On 31 March 1993, police and military witnesses across central England reported bright lights, more than 30 sightings in six hours. National Archives, 2009 files
  101. 101 Most of those 1993 sightings turned out to be a Russian rocket, which had launched the Cosmos 2238 satellite, burning up as it re-entered the atmosphere. National Archives, 2009 files
  102. 102 In 1993–94, dozens of Londoners reported a brightly lit oval object. It was an advertising airship, and some people refused to believe it. National Archives, 2009 files
  103. 103 Not everything is solved: an account in the MoD files of objects tracked by NATO radars and F-16 fighters over Belgium in 1990 says they remain unexplained. National Archives, 2009 files
  104. 104 The Ministry of Defence closed its UFO hotline and email address on 1 December 2009. The Independent
  105. 105 The MoD said it “has no opinion on the existence or otherwise of extra-terrestrial life”, but that in over 50 years no UFO report had shown any evidence of a threat to the UK. The Independent
  106. 106 It said there was no defence benefit in investigating sightings. The Independent
  107. 107 Ring the old number and a recording told you it was no longer MoD policy to record, respond to or investigate UFO sightings. The Guardian
  108. 108 The Guardian put the number of sightings the unit had dealt with at more than 11,000. The Guardian
  109. 109 The MoD has published lists of the UFO reports it received from 1997 to 2009, with dates, times, places and a short description. GOV.UK
  110. 110 One 2004 report from Douglas, Isle of Man, described a silver disc with solar panels. It turned out to be a twin-propeller ATR 42 Euromanx aeroplane. MoD UFO reports 2004
  111. 111 On 19 April 2001 someone on the Isle of Man reported three very large objects flying in formation, which split up and headed off south-east. MoD UFO reports 2001
  112. 112 In April 2020 the US Defense Department officially released three unclassified Navy videos: one from November 2004 and two from January 2015. US Defense Dept, 2020
  113. 113 The videos had already been circulating after unauthorised releases in 2007 and 2017. US Defense Dept, 2020
  114. 114 It released them to clear up confusion about whether the footage was real, or whether there was more to it. US Defense Dept, 2020
  115. 115 The Department said the things seen in the videos remain characterised as “unidentified”. US Defense Dept, 2020
  116. 116 One, known as the Gimbal video, was filmed by fighter pilots with the USS Theodore Roosevelt carrier group off the US East Coast in 2014–15. Britannica
  117. 117 Another, the GoFast video, seems to show a small object skimming above the ocean at great speed. NASA UAP study
  118. 118 NASA’s study team used the numbers on the display to work out that the object was at about 13,000 feet, more than four miles above the sea behind it. NASA UAP study
  119. 119 The impression of speed comes at least partly from the fast-moving jet itself, about 435 mph, plus parallax. NASA UAP study
  120. 120 The object moved about 390 metres in 22 seconds, roughly 40 mph: a typical wind speed at that height. NASA UAP study
  121. 121 The object was colder than the ocean, so there was no sign of heat from an engine. It was most likely drifting with the wind. NASA UAP study
  122. 122 NASA added that more data would allow a firmer conclusion. NASA UAP study
  123. 123 AARO explains that motion parallax can make a still or slow object look fast to a fast-moving observer: the background rushes past, not the object. AARO FAQ
  124. 124 Asked whether it has found any evidence of extraterrestrial technology, the US Defense Department’s AARO answers: “No.” It says examination of sightings is ongoing. AARO FAQ
  125. 125 AARO says no single explanation covers most UAP reports. AARO FAQ
  126. 126 Civilian pilots are encouraged to report UAP sightings to air traffic control. AARO FAQ
  127. 127 AARO says it will announce when there is a way for the public to report. AARO FAQ
  128. 128 In March 2024 AARO published a review of nearly 80 years of US government work on UAP, going back to 1945. US Defense Dept, 2024
  129. 129 It found no verifiable evidence that any UAP sighting was extraterrestrial activity. US Defense Dept, 2024
  130. 130 It found no verifiable evidence that the US government or private companies ever had access to alien technology. US Defense Dept, 2024
  131. 131 Every official investigation, at every level of secrecy, concluded that most sightings were ordinary objects and misidentifications. US Defense Dept statement
  132. 132 AARO looked at claims from about 30 people it interviewed. US Defense Dept, 2024
  133. 133 It put claims of hidden alien-technology programmes down largely to “circular reporting”: a small group repeating inaccurate stories heard from others over decades. US Defense Dept, 2024
  134. 134 AARO said it believed most of the people repeating the claims did so sincerely, without any wish to mislead. US Defense Dept, 2024
  135. 135 AARO’s report for May 2023 to June 2024 covered 757 UAP reports. US Defense Dept, 2024 report
  136. 136 Its director said AARO had resolved hundreds of cases to everyday things such as balloons, birds, drones, satellites and aircraft. US Defense Dept, 2024 report
  137. 137 He said only a very small percentage of reports are potentially anomalous. US Defense Dept, 2024 report
  138. 138 He also said AARO had found no verifiable evidence of extraterrestrial beings, activity or technology. US Defense Dept, 2024 report
  139. 139 More than 900 reports lacked enough scientific data to analyse, and are kept in case new information turns up. US Defense Dept, 2024 report
  140. 140 AARO says reports cluster near US military bases and sensors. US Defense Dept, 2024 report
  141. 141 AARO’s director said reports near national security sites must be taken seriously and investigated scientifically, because unidentified objects can be a safety risk. US Defense Dept, 2024 report
  142. 142 In one resolved case, infrared video turned out almost certainly to be birds: the infrared glow pulsed at the rate of wing beats. AARO imagery
  143. 143 In others, objects drifting at the speed and direction of the wind were judged almost certainly to be balloons. AARO imagery
  144. 144 Some cases stay unresolved simply because the footage is too poor, such as 30 seconds of mobile phone video. AARO imagery
  145. 145 NASA’s independent study team (2023) said there is, to date, no conclusive evidence in the peer-reviewed scientific literature that UAP come from beyond Earth. NASA UAP study
  146. 146 It said extraterrestrial life must be the explanation of last resort, used only after every other possibility is ruled out. NASA UAP study
  147. 147 NASA’s study team published its final report on 14 September 2023. NASA Science
  148. 148 The US Defense Department received 247 new UAP reports between March 2021 and August 2022, compared with 263 in the 17 years before. NASA UAP study
  149. 149 By 2023 AARO had collected more than 800 reported events. NASA UAP study
  150. 150 NASA’s team said the stigma around reporting UAP is an obstacle, and that its own involvement could help reduce it. NASA UAP study
  151. 151 It suggested smartphone apps that collect pictures and sensor data from many observers at once. NASA UAP study
  152. 152 Venus is one of the most confused objects in the sky, especially when it is low near the horizon. NASA Night Sky Network
  153. 153 Venus is the third brightest object in the sky, after the Sun and the Moon. NASA, Venus
  154. 154 A bright light such as Venus often seems to move, and can even seem to “follow” a car. Britannica
  155. 155 Sirius, Jupiter and Mercury are also often reported as UFOs, and bright planets lined up near the horizon can look like a formation of strange lights. NASA Night Sky Network
  156. 156 Other “UFOs” can be rocket launches, comets, military jets, weather balloons, satellites, meteors and fireballs, and odd clouds. NASA Night Sky Network
  157. 157 AARO says bright planets like Venus and Jupiter, and meteors, can look as if they are hovering or manoeuvring. AARO FAQ
  158. 158 High-altitude balloons for weather and research often have no markings and can look strange from some angles. AARO FAQ
  159. 159 The US National Weather Service alone launches hundreds of balloons a day; worldwide, thousands go up every day. AARO FAQ
  160. 160 Windblown plastic bags, foil party balloons and birds can look odd because of their small size and unpredictable motion; even radar can be fooled. AARO FAQ
  161. 161 Ordinary planes can look strange from unusual angles, in poor visibility or through infrared cameras. AARO FAQ
  162. 162 Drones can move erratically and fast, may have no visible lights, and are often too small for radar to classify. AARO FAQ
  163. 163 Some remote-control model aircraft are even built to look like flying saucers. NASA Night Sky Network
  164. 164 Rocket launches can leave glowing spirals and lingering exhaust plumes high in the sky. AARO FAQ
  165. 165 Sunlight flashing off a satellite’s solar panels can make a bright light that is often mistaken for a fast UAP or an “orb”. AARO FAQ
  166. 167 Before they spread out, a new batch circles Earth as a “train” that looks like a long string of bright lights. Skeptical Inquirer, Starlink
  167. 168 When the first trains appeared in May 2019 they were often reported as UFOs, including by airline pilots. Skeptical Inquirer, Starlink
  168. 169 A satellite high overhead can still be in sunlight when it’s dark on the ground, which is why trains show up just after sunset or before sunrise. Skeptical Inquirer, Starlink
  169. 170 In 2022, pilots reported pulsing “racetrack” lights circling far away; amateur investigators matched every video they could date and place to Starlink satellites. Skeptical Inquirer, Starlink
  170. 171 Lenticular clouds form downwind of hills and mountains, look a lot like science-fiction flying saucers, and are thought to be one of the most common explanations for UFO sightings worldwide. Met Office
  171. 172 They are quite unusual in the British Isles, but do sometimes appear. Met Office
  172. 173 Camera lenses can turn a single point of light into something that looks saucer-shaped. Britannica
  173. 174 Some photo “UFOs” are lens flare or other camera artefacts. NASA Night Sky Network
  174. 175 Reflections in windows and glasses can overlay one view on another. Britannica
  175. 176 Judging the distance and speed of a light in a blank sky is very unreliable, because there is nothing to compare it with. Britannica
  176. 177 Radar is more reliable in some ways, but can’t always tell aircraft from meteor trails, rain or layers of warm and cold air. Britannica
  177. 178 At least some sightings have been hoaxes. Britannica
  178. 179 Most psychologists who have studied “alien abduction” stories doubt they involve aliens, and point to a common experience called sleep paralysis. Britannica
  179. 180 Compressing video adds artefacts to it, so AARO wants original, uncompressed camera files. AARO FAQ
  180. 181 If you know the date, time and direction, free planetarium software such as Stellarium can show what was in the sky. NASA Night Sky Network
  181. 182 Your local astronomy club can help, so note the date and time, how long you watched, its path and speed, and how bright it was. NASA Night Sky Network
  182. 183 If you saw it long after sunset, it is less likely to have been a sunlit balloon or an unlit aircraft. NASA Night Sky Network
  183. 184 Check for recent meteor showers and things that are common in your area. NASA Night Sky Network
  184. 185 NASA’s skywatching team says it is important to be respectful about other people’s sightings, because everyone who looks up long enough sees something they can’t explain at first. NASA Night Sky Network
  185. 186 Their goal is to turn a UFO into an IFO: an identified flying object. NASA Night Sky Network
  186. 187 Investigators say the most useful thing is to record the time and the location of both you and the object. AARO FAQ
  187. 188 With a time and place, a sighting can be checked against air traffic, balloon-tracking and satellite-tracking records. AARO FAQ
  188. 189 Phone photos carry useful hidden data, such as GPS position and time stamps. AARO FAQ
  189. 190 NASA’s team said eyewitness reports can be interesting and compelling, but can’t be reproduced and usually lack the details needed for a firm answer. NASA UAP study