Within Baselines
When Ordinary Aircraft Slip Through the Net
A baseline archive must include known aircraft the system failed to match, because missed traffic can look more mysterious than detected traffic.
On this page
- Why aircraft may not appear in comparison data
- How missed matches distort anomaly rates
- What detector logs should preserve after a miss
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Introduction
An automated instrumented UFO detector is only as good as its ability to recognise ordinary aircraft. A common misunderstanding is that if an aircraft does not appear in a comparison database such as ADS-B (Automatic Dependent Surveillance–Broadcast), it was probably not an aircraft. In reality, comparison data are powerful but incomplete. Aircraft may be absent because they are outside receiver coverage, not required to broadcast in that airspace, experiencing equipment or reception problems, or deliberately limiting the visibility of their transmissions in certain circumstances. If a detector mistakes “not matched” for “not an aircraft”, ordinary flights can become false UAP candidates. NASA’s independent UAP study stressed that robust metadata, calibrated instruments and richer baseline data are essential precisely because incomplete comparison information can produce misleading anomalies. [NASA Science]science.nasa.govScience Independent Study Team ReportNASA ScienceIndependent Study Team ReportSeptember 13, 2023 — The study of Unidentified Anomalous Phenomena (UAP) presents a unique scien…
For a pattern-of-life archive, the important lesson is that unmatched aircraft should become part of the baseline rather than being discarded. Recording how and why known aircraft escaped automatic identification improves future classification and prevents inflated anomaly statistics.
Why aircraft may not appear in comparison data
Aircraft comparison systems depend on several independent links working correctly. A failure anywhere along that chain can produce an apparent mystery even when the object itself is entirely ordinary.
Some of the most common causes include:
- Incomplete ADS-B coverage. Ground receivers have geographical blind spots. Mountains, terrain masking, low-altitude flight and sparse receiver networks reduce reception quality. Oceanic and remote regions remain especially challenging without satellite-based surveillance. [ResearchGate]researchgate.netResearch Gate(PDF) A method for estimating flight paths missing dataResearchGate(PDF) A method for estimating flight paths missing dataNovember 8, 2018 — This paper proposes a method based on artificial ne…
- Reception dropouts. Even where coverage exists, communication losses occur in real flight operations. Studies analysing operational radar and ADS-B data have documented temporary losses lasting from brief interruptions to longer gaps, meaning a comparison system may temporarily lose an otherwise identifiable aircraft. [MDPI]mdpi.comAnalysis of Radar and ADS-B Influences on Aircraft Detect…by W Semke · 2017 · Cited by 38 — We examined the occurrence and duratio…
- Regulatory differences. Not every aircraft is required to broadcast ADS-B in every type of airspace. Requirements vary between countries, flight rules and operating environments, meaning an absence from public tracking services does not automatically imply unusual activity. [Federal Aviation Administration+2Airservices]faa.govFederal Aviation AdministrationFrequently Asked Questions | Federal Aviation Administration1 Aug 2025 — In order to comply with 14 CFR 91…
- Military and government operations. Some authorised operations may not appear consistently on public aggregation websites because of operational practices, receiver availability or restrictions on redistributed data. Public flight-tracking services are not identical to the surveillance picture available to air traffic authorities. [Reddit]reddit.comreasons we door dontsee military aircraftReasons we do—or don't—see military aircraft: r/ADSBFebruary 10, 2022 — It seems like American military planes are generally ADS-B…
- Aggregation limitations. Popular flight-tracking websites combine data from thousands of volunteer receivers. Their displayed tracks are reconstructed products rather than a perfect census of every aircraft overhead, so local gaps should be expected. [ResearchGate]researchgate.netResearch Gate(PDF) A method for estimating flight paths missing dataResearchGate(PDF) A method for estimating flight paths missing dataNovember 8, 2018 — This paper proposes a method based on artificial ne…
The practical consequence is that “no ADS-B match” and “not an aircraft” are fundamentally different conclusions. The former is an observation about the comparison dataset, not about the object itself.
How missed matches distort anomaly rates
The most damaging effect of missed aircraft is statistical rather than visual. Every unmatched aircraft artificially increases the apparent number of unexplained events.
Consider a detector that records one hundred moving objects during a night.
- Ninety-five match aircraft records.
- Three are birds.
- One is a satellite.
- One aircraft fails to match because of a reception gap.
If unmatched targets are automatically counted as anomalous, the detector reports one unexplained object despite every observation having a conventional explanation. Over months of operation, these false anomalies accumulate and create the impression that genuinely unexplained events are more common than they really are.
This distortion is particularly problematic when evaluating detector performance. A system with excellent optical sensors but poor aircraft correlation software may appear to discover more UAPs simply because it misses more ordinary traffic.
Pattern-of-life collection therefore measures not only what was successfully identified, but also the detector’s identification failure rate. Knowing that, for example, 2% of aircraft are routinely missed under certain weather conditions is valuable calibration information.
Why unmatched aircraft often look more mysterious
A missed aircraft frequently appears more unusual than a successfully identified one because contextual information disappears.
Without a correlated flight track, investigators lose:
- aircraft identity;
- flight plan context;
- expected speed and heading;
- altitude estimates from surveillance data;
- confirmation that navigation lights or landing lights should be visible;
- an independent timing reference.
The remaining camera footage may show only a bright moving light whose apparent behaviour is strongly influenced by camera zoom, atmospheric refraction, autofocus changes or tracking algorithms.
Because human observers naturally seek explanations, missing contextual data can make an otherwise ordinary aircraft appear to accelerate, hover or manoeuvre unexpectedly. The mystery often originates in missing metadata rather than unusual flight behaviour.
NASA’s UAP study repeatedly emphasised that richer contextual measurements reduce false anomalies because they allow investigators to reconstruct the full observational environment instead of analysing isolated imagery. [NASA Science]science.nasa.govScience Independent Study Team ReportNASA ScienceIndependent Study Team ReportSeptember 13, 2023 — The study of Unidentified Anomalous Phenomena (UAP) presents a unique scien…
What detector logs should preserve after a miss
A mature automated detector should treat every failed aircraft correlation as a diagnostic event rather than simply flagging an anomaly.
Useful logs include:
- the complete sensor recording before, during and after the missed match;
- the exact comparison databases queried and their timestamps;
- receiver health and ADS-B reception statistics;
- weather, cloud cover and visibility;
- antenna status and signal quality;
- camera pointing direction and calibration state;
- confidence scores from the matching algorithm;
- whether the object was later matched retrospectively using updated traffic data.
Retrospective correlation is especially valuable because some aircraft tracks become available only after delayed data processing or through higher-quality archives than those available in real time. Preserving the original observation allows investigators to determine whether the anomaly resulted from a genuine unknown object or from an incomplete comparison dataset.
Designing baseline archives that learn from misses
The strongest pattern-of-life collections do not simply archive successful identifications; they also archive failures.
Instead of storing only “matched aircraft”, an effective baseline records:
- unmatched moving targets later confirmed as aircraft;
- geographical areas where aircraft matches regularly fail;
- weather conditions associated with poor correlation;
- receiver outages and communication dropouts;
- software versions used during matching;
- recurring aircraft classes that are frequently missed.
Over time these records become a detector performance database rather than merely a sky catalogue. Engineers can identify systematic weaknesses—for example, persistent failures below a certain elevation angle or during heavy precipitation—and improve future matching algorithms.
The baseline therefore evolves in two directions simultaneously: it becomes a better description of the local sky, and a better description of the detector’s own limitations.
The practical takeaway
For automated instrumented UFO detection, missed aircraft are not merely unavoidable noise; they are one of the most informative classes of false UAP candidate. An unmatched aircraft demonstrates the gap between the real sky and the detector’s comparison system. Treating those events as calibration opportunities rather than unexplained phenomena prevents ordinary aviation from inflating anomaly rates, improves future identification accuracy and produces a more trustworthy pattern-of-life archive.
Amazon book picks
Further Reading
Books and field guides related to When Ordinary Aircraft Slip Through the Net. Use these as the next step if you want deeper reading beyond the article.
The Demon-Haunted World
Strong fit for the page’s warning that missing comparison data is not proof of anomaly.
How to Measure Anything
Explains uncertainty, measurement gaps, and how to reason from incomplete evidence.
Stick and Rudder
Gives readers practical aviation context for ordinary aircraft behaviour and appearances.
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Endnotes
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Source: science.nasa.gov
Title: Science Independent Study Team Report
Link: https://science.nasa.gov/wp-content/uploads/2023/09/uap-independent-study-team-final-report.pdfSource snippet
NASA ScienceIndependent Study Team ReportSeptember 13, 2023 — The study of Unidentified Anomalous Phenomena (UAP) presents a unique scien...
Published: September 13, 2023
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Source: researchgate.net
Title: Research Gate(PDF) A method for estimating flight paths missing data
Link: https://www.researchgate.net/publication/328831194_A_method_for_estimating_flight_paths_missing_dataSource snippet
ResearchGate(PDF) A method for estimating flight paths missing dataNovember 8, 2018 — This paper proposes a method based on artificial ne...
Published: November 8, 2018
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Source: mdpi.com
Link: https://www.mdpi.com/2226-4310/4/3/49Source snippet
Analysis of [Radar]({{ 'radar/' | relative_url }}) and ADS-B Influences on Aircraft Detect...by W Semke · 2017 · Cited by 38 — We examined the occurrence and duratio...
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Source: researchgate.net
Link: https://www.researchgate.net/publication/319908709_Analysis_of_Radar_and_ADS-B_Influences_on_Aircraft_Detect_and_Avoid_DAA_SystemsSource snippet
Analysis of Radar and ADS-B Influences on Aircraft Detect...We examined the occurrence and duration of communication losses between rada...
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Source: reddit.com
Title: reasons we door dontsee military aircraft
Link: https://www.reddit.com/r/ADSB/comments/sp0id2/reasons_we_door_dontsee_military_aircraft/Source snippet
Reasons we do—or don't—see military aircraft: r/ADSBFebruary 10, 2022 — It seems like American military planes are generally ADS-B...
Published: February 10, 2022
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Source: reddit.com
Title: Unpopular opinion but see and avoid is not enough
Link: https://www.reddit.com/r/flying/comments/1u7r64m/unpopular_opinion_but_see_and_avoid_is_not_enough/Source snippet
r/flyingNone had ADSB-out. i am building a prototype and I was astonished comparing with FlightRadar24 about the amount of aircraft flyin...
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Source: faa.gov
Link: https://www.faa.gov/air_traffic/technology/equipadsb/resources/faqSource snippet
Federal Aviation AdministrationFrequently Asked Questions | Federal Aviation Administration1 Aug 2025 — In order to comply with 14 CFR 91...
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Source: airservicesaustralia.com
Link: https://www.airservicesaustralia.com/wp-content/uploads/FAQ_ADS-B_DEC16.pdf -
Source: infrastructure.gov.au
Link: https://www.infrastructure.gov.au/sites/default/files/documents/adsb-101-anonymous.pdfSource snippet
AnonymousIn complex or busy environments in non-controlled airspace, ADS-B can be a potential cost-effective mechanism for improving serv...
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Source: faa.gov
Title: A321 Workaround SRM Document
Link: https://www.faa.gov/sites/faa.gov/files/A321%20Workaround%20SRM%20Document.pdfSource snippet
Using the “A321” ICAO type designator signifies the aircraft's capability...Read more...
Additional References
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Source: icao.int
Link: https://www.icao.int/sites/default/files/APAC/Meetings/2025/2025%20ICAO%20APAC%20Radio%20Navigation%20Symposium%20%20Radio%20N/8-Risks%20Beyond%20GNSS/SP22-ADS-B-spoofing-and-mitigating-measures.pdfSource snippet
ADS-B spoofing and mitigating measuresBroadcasting of ADS-B messages by aircraft transponder. Threat: Malware may be installed onto the a...
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Source: eoportal.org
Link: https://www.eoportal.org/other-space-activities/ads-bSource snippet
ADS-B (Automatic Dependent Surveillance-Broadcast)ADS-B Only [satellites]({{ 'satellites/' | relative_url }}) have the capability to provide a global coverage at any possible...
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Source: icao.int
Link: https://www.icao.int/sites/default/files/sp-files/APAC/Documents/Meetings/2006/adsb_sitf5rpt.pdfSource snippet
REPORT OF ADS-B SEMINAR AND THE FIFTH MEETING...ADS-B monitoring. 8.9. Analysis on the raw ADS-B reports from aircraft monitored by two...
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Source: avi-loeb.medium.com
Title: a new calculation on the fly to the nasa uap study 2dacaf860cac
Link: https://avi-loeb.medium.com/a-new-calculation-on-the-fly-to-the-nasa-uap-study-2dacaf860cacSource snippet
New Calculation on the Fly to the NASA UAP Study - Avi LoebThe NASA Study will examine unclassified data on UAP in an attempt to separate...
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Source: assureuas.org
Title: GP S & ADS-B Risks for UAS (A44_A11L.UA S.86)
Link: https://www.assureuas.org/projects/gps-ads-b-risks-for-uas/Source snippet
GPS & ADS-B Risks for UAS (A44_A11L.UAS.86) - AssureErroneous, spoofed, jammed, or drop outs of “ADSB-In” data may result in automated un...
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Source: acronaviation.com
Title: How ADS-B In Is Transforming U.S
Link: https://acronaviation.com/newsroom/beyond-radar-how-ads-b-in-is-shaping-the-future-of-us-aviation-operations/Source snippet
Aviation Operations23 Jul 2025 — Unlike traditional systems that rely solely on radar and ATC voice instructions, ADS-B In delivers real...
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Source: facebook.com
Link: https://www.facebook.com/fox12oregon/posts/the-bill-would-require-all-aircraft-to-be-equipped-with-a-system-that-can-receiv/1357436346424275/Source snippet
ave the siting limitations of radar. Its accuracy...
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Source: vansairforce.net
Link: https://vansairforce.net/threads/the-ads-b-system-is-flawed.116633/Source snippet
he clear continuously, not just when triggered...
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Source: aviation.stackexchange.com
Title: how can ads b be secure when it is based on self reporting
Link: https://aviation.stackexchange.com/questions/13459/how-can-ads-b-be-secure-when-it-is-based-on-self-reportingSource snippet
In the simplest definition, ADS-B is aircraft self-reporting GPS position to benefit everyone...
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Source: aviation.govt.nz
Link: https://www.aviation.govt.nz/safety/safety-education-and-advice/education/vector-magazine/vector-online/limitations-of-adsb/Source snippet
ADS-B IN allows an aircraft...Read more...
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