THE DOCUMENT
CIA-UAP-015, “Project Blue Book Special Report No. 14”, is a document from the U.S. Department of War’s PURSUE Release 03, published at war.gov/ufo, cleared 12 June 2026. Its own title page reads “PROJECT BLUE BOOK / SPECIAL REPORT NO. 14 / (ANALYSIS OF REPORTS OF UNIDENTIFIED AERIAL OBJECTS)”, issued by the Air Technical Intelligence Center at Wright-Patterson Air Force Base and dated 5 May 1955. It is the statistical study the U.S. Air Force commissioned of the unidentified-aerial-object reports it had collected from mid-1947 to the end of 1952.
Why this one is worth your time
This is the document most often cited, by all sides, when people argue about what the government’s own UFO files showed. It is not a sighting report. It is the Air Force counting and sorting its own backlog: roughly 3,200 cases, run through a punched-card statistical study and a chi-square test, to ask whether the leftover “unknowns” looked like anything other than misidentified ordinary things. The report reaches a clear conclusion and states it plainly, and it also records exactly how many cases it could not identify. This briefing sets out both, in the document’s own words.
What the document says
What kind of study this is. The report is the published result of a study commissioned by the Air Force and dated 5 May 1955. The reports the Air Force had received were reduced to IBM punched-card abstracts using standardised forms, and the study set out, in its own summary, to “discover any pertinent trend or pattern inherent in the data” and to “determine the probability that any of the UNKNOWNS represent observations of technological developments not known to this country”. The dataset was closed off at the end of 1952; the report states that “In these charts, 3201 cases have been used.”
The classification scheme. Each sighting was evaluated and assigned to an identification category. The report groups these categories into two sets, “the KNOWNS (including all identification categories except the UNKNOWNS) and the UNKNOWNS.” Known categories covered the ordinary candidates: balloons, aircraft, astronomical bodies, birds, clouds or dust, an OTHER category for less common objects, and a LIGHT PHENOMENON category. Two further categories sat apart. INSUFFICIENT INFORMATION was assigned where some essential item of information was missing, and the report states it “was not used as a convenient way to dispose of what might be called ‘poor unknowns’, but as a category for reports that, perhaps, could have been one of several known objects or natural phenomena.” UNKNOWN was reserved for reports where “the description of the object and its maneuvers could not be fitted to the pattern of any known object or phenomenon.” Known identifications were further marked “Certain” or “Doubtful”.
How many were unknowns. The study presented the data on several different bases. On the basis of OBJECT SIGHTINGS (2,199 cases), the report’s Figure 2 records the unknowns as “474 = 21.5%”. The report also tracked later cases as a check: it states that the 1953 and 1954 reports showed “increasing percentages in the finally identified categories” and “decreasing percentages” of insufficient-information and unexplained cases, and that under a revised, faster investigation programme the unknown cases had been reduced “to 3%, of the totals” by 1955.
The chi-square test of knowns versus unknowns. Mirror graphs had seemed to suggest that, grouped by characteristics such as colour, number, shape, duration, speed and brightness, “the UNKNOWNS were no different from the KNOWNS, at least in the aggregate.” The report says it decided to test this with a statistical procedure, the Chi Square Test, which it describes as “a statistical test of the likelihood that two distributions come from the same population.” Applied across the six characteristics (Tables II through VII, and revised versions in Tables VIII through XIII), the test pointed the other way: the report states the tests “showed that there was a low probability that the distributions of the KNOWNS, and UNKNOWNS by these characteristics were the same.” In other words, on the report’s account, the unknowns did not statistically match the knowns.
The search for a “flying saucer” model. Separately, the study tried to build a description of a “flying saucer” from the best unknown cases. The report defines the term for its own purposes as “a novel, airborne phenomenon, a manifestation that is not a part of or readily explainable by the fund of scientific knowledge known to be possessed by the Free World.” It records that out of about 4,000 people who reported a “flying saucer”, sufficiently detailed descriptions were given in only 12 cases, that those 12 could not be reconciled into a single model, and that no groups of unknowns sharing the same characteristics could be found.
The report’s own conclusions. The Conclusions section opens with the statement that “It can never be absolutely proven that ‘flying saucers’ do not exist.” It attributes the failure to identify the unknowns to “a combination of factors, principally the reported maneuvers of the objects and the unavailability of supplemental data such as aircraft flight plans or balloon-launching records.” It emphasises “a complete lack of any valid evidence consisting of physical matter in any case of a reported unidentified aerial object.” And it states its conclusion on the central question directly: that “the probability that any of the UNKNOWNS considered in this study are ‘flying saucers’ is concluded to be extremely small”, and that it is “highly improbable that any of the reports of unidentified aerial objects examined in this study represent observations of technological developments outside the range of present-day scientific knowledge.”
What the document does not say
It does not claim certainty in either direction. The report states in its own conclusions that the non-existence of “flying saucers” can never be absolutely proven, and frames its findings as probabilities (“extremely small”, “highly improbable”) drawn from the data it had, not as proof.
It records the limits of its own data. The report says the original reports “seldom contained reliable measurements of physical attributes”, that this subjectivity “presented a major limitation to the drawing of significant conclusions”, and that the incompleteness of a large proportion of the reports “may have obscured any patterns or trends that otherwise would have been evident.”
It does not resolve the individual unknowns. The 474 object-sighting unknowns, and the 12 best-detailed cases, are left unidentified by the study; the report concludes only that they failed to form a model or a pattern, not that each one was explained. The chi-square finding that the unknowns differed statistically from the knowns is stated as a result, and the report does not say what the unknowns were.
The figures here are this report’s own. The 3,201-case set and the 21.5% unknown proportion are Special Report No. 14’s, drawn from 1947 to 1952 data. They are not the same as the often-quoted Project Blue Book lifetime totals (12,618 sightings, 701 “unidentified”) that appear on the later NASA fact sheet covered in the Congress-White House 1998 briefing; the two come from different sources and different periods.
From the record
PROJECT BLUE BOOK SPECIAL REPORT NO. 14 The document’s own title page
UNKNOWN - This designation in the identification code was assigned to those reports of sightings wherein the description of the object and its maneuvers could not be fitted to the pattern of any known object or phenomenon. The report’s definition of the UNKNOWN category
The Chi Square Test is a statistical test of the likelihood that two distributions come from the same population, that is, it gives the probability that there is no difference in the make-up of the two distributions being measured. The report describing its statistical method
It can never be absolutely proven that “flying saucers” do not exist. The opening line of the report’s Conclusions
It is emphasized that there was a complete lack of any valid evidence consisting of physical matter in any case of a reported unidentified aerial object. The report’s Conclusions
Thus, the probability that any of the UNKNOWNS considered in this study are “flying saucers” is concluded to be extremely small, since the most complete and reliable reports from the present data, when isolated and studied, conclusively failed to reveal even a rough model, and since the data as a whole failed to reveal any marked patterns or trends. The report’s Conclusions
Therefore, on the basis of this evaluation of the information, it is considered to be highly improbable that any of the reports of unidentified aerial objects examined in this study represent observations of technological developments outside the range of present-day scientific knowledge. The closing conclusion of the report
Where the case connects
The report sits next to the Robertson Panel material in this release. Special Report No. 14 is the larger statistical study that followed in the same period; the Robertson Panel briefing (Briefing 6 of Release 03) covers the 1953 scientific review of UFO evidence, and the two documents address the same Air Force backlog from different angles. The report’s Blue Book figures here (about 3,200 cases, 21.5% unknown on the object-sightings basis) are also worth reading alongside the lifetime Blue Book totals (12,618 sightings, 701 “unidentified”) quoted on the NASA fact sheet in the Congress-White House 1998 briefing, which come from a different source and a longer span. Briefing 1 of Release 01 covers PURSUE and the tier system.
The report also leaves its own loose ends. It identifies neither the 474 object-sighting unknowns nor the 12 best-detailed cases; it states that supplemental data such as flight plans and balloon-launch records were unavailable for many cases; and its chi-square finding that the unknowns differed from the knowns is recorded without an account of what the unknowns were. Any later release of the underlying case files, the working papers, or a re-analysis of this dataset lands in this series when it does.
Read it yourself
CIA-UAP-015, “Project Blue Book Special Report No. 14”, is hosted at war.gov in PURSUE Release 03.
Read the file. Decide for yourself.
Related wiki entries
The wiki entries below give background on the programme and the publisher behind this briefing.
References and further reading
- Primary document: CIA-UAP-015, “Project Blue Book Special Report No. 14”, PURSUE Release 03, U.S. Department of War, hosted at war.gov/ufo
- Presidential Unsealing and Reporting System for UAP Encounters, U.S. Department of War, war.gov/ufo
- AARO UAP Records, All-domain Anomaly Resolution Office, aaro.mil/UAP-Records
- Briefing 6 of Release 03, on the Robertson Panel and the 1953 scientific review
- Briefing 14 of Release 03, on the Congress-White House 1998 correspondence and the NASA Blue Book fact sheet
- Briefing 1 of Release 01, on PURSUE and the evidence tier system