You Should Know: Luis Elizondo's Five Observables

"It doesn't matter what I believe. What matters is what the data and the facts tell us."

The early days of UFO investigation were marked by a credibility problem. With no widely available cameras and limited sensor data, analysis tended to focus mainly on “who was reporting something,” and “should we believe them?”

That all changed when the Department of Defense (DoD) began to re-engage with UFOs in 2008. Now, the most advanced sensors and recording equipment in the world were unmistakably picking up something. Inside the Pentagon questions moved from “who and when” to “what is that” and “how?!”¹²

Here began a problem of separating the signal from the noise. Even though the United States military was encountering strange objects in its operating areas, it was still possible that they could be explained in some terrestrially conventional way. Foreign adversaries had been known to observe U.S. training exercises and the United States remains at the leading edge of experimental aircraft development.

To try and carve out the truly unexplainable incidents, a DoD team led by Luis Elizondo developed a filtering mechanism that is still widely used today. These “Five Observables,” as they came to be called, were common to many of their most extraordinary reports, had been consistently observed since the 1940s, and seemed to point to a technology that was well beyond our current understanding and capability.³

Filtering UFO cases with these simple, well-defined criteria went a long way to adding credibility to their work, but, ultimately, it wasn’t enough to convince senior leadership to take it seriously. Luis Elizondo resigned as Director of the “Advanced Aerospace Threat Identification Program” (AATIP) in 2017, and as he left the Pentagon, he brought his thinking, and the Five Observables out into the public eye.⁴

While originally popularized on the History Channel’s 2019 TV show Unidentified, the Five Observables have since taken on a life of their own.⁵ Today, they serve as one of the UFO Community’s most important tools when it comes to deciding which cases to take seriously and which ones to ignore. And if you find yourself with even a passing interest in UFOs, you should know …

The Five Observables

What are the Five Observables? In their most current interpretation, they are:

1. Positive Lift – The ability to fly without apparent means of propulsion or lift.

2. Instantaneous Acceleration – The ability to reach a high rate of speed in a very short amount of time.

3. Hypersonic Velocity (Without Signatures) – The ability to travel faster than five times the speed of sound (3,700 mph) with no accompanying auditory or physical effects.

4. Trans-Medium Travel – The ability to seamlessly move through space, air, and water.

5. Low Observability – The ability to conceal from visual and sensor observation.⁶⁷

Turning to each of these observables in more detail, we begin with:

Positive Lift

Lift is the mechanical force that holds an aircraft in the air. Generally speaking, an aircraft needs to change its relationship to our surrounding air (by being in motion) and it needs to turn the flow of air in one direction (to generate lift). Our most common aircraft use propellors, jet engines, or chemical explosions to generate motion and a variety of control surfaces, like wings, to generate lift.⁸

This observable applies when we see an object that is flying with no obvious means of achieving that positive lift. This happens when we don’t see any propulsion mechanism (like a jet engine), we don’t see any control surfaces (like wings), and we don’t see any of the heat signatures that almost all aircraft would generate when going through this process.

Additionally, our technology is still very limited in terms of the kind of flight we can achieve. Flight time is not infinite, and we are effectively unable to bring an aircraft to a complete stop (or hover) mid-air. Objects in this category have been observed hovering mid-air, flying for extremely long periods of time, and often outlasting the jets that are sent to investigate them before they run low on fuel.⁹

Instantaneous Acceleration

The fastest accelerating aircraft in the world is the Lockheed SR-71 Blackbird, which was used to spy on the Soviet Union during the Cold War. In 12 minutes, the aircraft could go from a dead stop to 3.2 times the speed of sound.¹⁰ The aircraft, which could withstand a maximum of 3 g’s during this process,¹¹ is effectively the pinnacle of human achievement when it comes to acceleration. There is no aircraft that’s been able to outperform it and anything carrying a human being has a hard limit of 9 g’s (the maximum number of “Earth Gravities” a human body can sustain).¹²

This observable applies to objects that seem to be achieving even better acceleration, in many cases from a complete stop. In one notable incident during the 2004 Nimitz Encounters, radar tracked an object descending from 28,000 ft to sea level in 0.78 seconds. This “instantaneous acceleration” (which really means acceleration that is almost too fast to measure) produced a travel speed of 60 times the speed of sound (46,000 mph) with an estimated 5,370 g’s.¹³ This is well beyond our known technology or the capabilities of a human body.

Hypersonic Velocity

While many aircraft are fast, very few can break the sound barrier without serious assistance. This makes hypersonic flight the domain of the military and experimental scientific craft like NASA’s scramjet program. Even if technology in the private sector improved to the degree where widespread hypersonic flight was possible, those flights would still be limited by the Federal Aviation Administration’s 1973 decision to ban all hypersonic flight over U.S. soil.¹⁴

Why did this ban happen? Because any aircraft breaking the sound barrier also tend to be quite noticeable. First, they generate a series of sonic booms when the air around the aircraft expands and contracts along its flight path.¹⁵ Second, the aircraft may drop off a deadly amount of energy when it comes to a complete stop (depending on its weight and stopping speed). When assessing the previously highlighted 0.78 second drop in the 2004 Nimitz Encounter, one academic calculated that the object should have produced an impact equivalent to 100 tonnes of TNT or 250 Tomahawk Missiles going off at once.¹⁶

This observable applies to objects that appear to be travelling faster than five times the speed of sound (which is the threshold for hypersonic velocity) and that seem to be producing no auditory or physical effects that we would expect to see from anything travelling at those speeds.

Trans-Medium Travel

We don’t really have vehicles that can seamlessly travel between the ocean, our atmosphere, and outer space. Our vehicles tend to be “purpose-built” to operate in the environment we need them too. Anything else would be financially impractical and might not even be possible with our current technology.¹⁷

Even though “Unidentified Flying Object” or “Unidentified Aerial Phenomena” would tend to imply observation in the air, modern UFOs have been observed travelling seamlessly through space, air, and water.¹⁸ This observable applies to objects that seem to demonstrate this trans-medium travel ability, which, to our knowledge, is not possible with any existing aircraft. In addition, the objects demonstrating this capability seem to be able to accomplish it without any obvious physical effects (like a space shuttle burning up on re-entry) or significant changes to speed.

Low Observability

This observable applies broadly to objects that are attempting to conceal their position. The kind of technology required to appropriately camouflage an aircraft, alter its visual profile, passively avoid sensor detection, or actively jam those sensors is limited to only a few militaries in the world. While acknowledging that conventional research and development is making significant progress in these areas,¹⁹ the low observability objects in the UFO space tend to be demonstrating an ability far beyond our current understanding.

In addition to this impressive potential, these objects also tend to be concealing themselves in a context that is hard to attribute to any domestic or foreign source. U.S. research and development programs do not test new abilities against uninformed military units.²⁰ When safety and security is assured through a pre-planned test, they still do not tamper with U.S. weaponry in a way that might alter defense readiness, with, say, our nuclear arsenal. Foreign adversaries are similarly disincentivized to deploy cutting edge technology in a way that could risk conflict or ultimately be captured by the United States. In that sense, low observability is as much about the context of the interaction as the difficulty in making an appropriate sensor or visual ID.

Moving Forward (at hypersonic velocity)

It’s likely that the Five Observables will continue to be a significant filter for deciding which UFO incidents deserve the most attention. And while Luis Elizondo can be credited with developing this framework, it’s also clear that it continues to evolve both inside and outside of government.

Recent work by Dr. Kevin Knuth (Associate Professor of Physics at the University of Albany) has gone a long way to clarifying these categories and updating their description to be more technically accurate. And if the recent “UAP Disclosure Act” is any indication, it appears the government is taking that seriously. All Five Observables have now worked their way into pending UFO legislation and if the United States Congress is going to use them to define “unidentified anomalous phenomena,” then perhaps we should too.

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P.S. Do you think this might be a good crash course for someone you know? Help them out and:

1. Burton, Charlie. Luis Elizondo on unidentified aerial phenomena, extraterrestrials and the Pentagon's UFO programme. Other. British GQ, November 25, 2021. https://youtu.be/4yX6ETCKyPo. At 48s.

2. Elizondo, Luis. “Luis Elizondo Presents the History of AATIP.” To The Stars Academy of Arts and Science, August 30, 2018. https://youtu.be/D3r6SmrCUM0?si=d2AluIHj9_SfA8L5. At 13min 48s.

3. Alemany, Jacqueline. “Transcript: UFOs & National Security with Luis Elizondo, Former Director, Advanced Aerospace Threat Identification Program.” The Washington Post, June 8, 2021. https://www.washingtonpost.com/washington-post-live/2021/06/08/transcript-ufos-national-security-with-luis-elizondo-former-director-advanced-aerospace-threat-identification-program/.

4. See Luis Elizondo’s resignation letter at “UFO Investigations: Revealing Documents from History’s ‘Unidentified.’” The History Channel, May 31, 2019. https://web.archive.org/web/20200724053320/https://www.history.com/news/unidentified-ufo-investigation-documents.

5. “The UFO Insiders.” Unidentified: Inside America’s UFO Investigation Season 1, Episode 1. The History Channel, May 31, 2019.

6. Knuth, Kevin. “UAP Flight Characteristics: The Five Observables.” Tim Ventura YouTube Channel, July 30, 2022. https://youtu.be/-FSaV3HleUY.

7. Carlson, Ryan. “Five Characteristics Unique to UAP’s.” To The Stars, Updated: January 21, 2022. https://tothestars.media/en-ca/blogs/press-and-news/five-characteristics-unique-to-uaps.

8. Benson, Tom. “What Is Lift?” NASA - Beginner’s Guide to Aeronautics, May 13, 2021. https://www.grc.nasa.gov/www/k-12/VirtualAero/BottleRocket/airplane/lift1.html.

9. Knuth, ““UAP Flight Characteristics: The Five Observables.” At 7min 35s.

10. “The Fastest-Accelerating Aircraft.” Defense Bridge, March 5, 2023. https://defensebridge.com/article/the-fastest-accelerating-aircraft.html#:~:text=With%20a%20cruising%20speed%20of,the%20world’s%20fastest%2Daccelerating%20aircraft.

11. “How Much G-Force Can the Human Body Withstand?” Sky Combat Ace, September 22, 2021. https://www.skycombatace.com/blog/human-body-g-force.

12. Cavelos, Jeanne. “The Jump to Light Speed Is a Real Killer.” Scientific American, August 11, 2008. https://www.scientificamerican.com/article/star-wars-science-light-speed/#:~:text=Normal%20humans%20can%20withstand%20no,heavier%20blood%20to%20the%20brain.

13. Knuth, Kevin H, Robert M Powell, and Peter A Reali. “Estimating Flight Characteristics of Anomalous Unidentified Aerial Vehicles in the 2004 Nimitz Encounter.” Proceedings, December 16, 2019. http://dx.doi.org/10.3390/proceedings2019033026. Pg 3.

14. Hutson, Matthew. “Will We Ever Fly Supersonically Over Land?” The New Yorker, June 25, 2021. https://www.newyorker.com/tech/annals-of-technology/will-we-ever-fly-supersonically-over-land.

15. “What Causes a Sonic Boom?” How Stuff Works, April 1, 2000. https://science.howstuffworks.com/question73.htm.

16. Knuth, “Estimating Flight Characteristics of Anomalous Unidentified Aerial Vehicles in the 2004 Nimitz Encounter.” Pg 9.

17. Tingley, Brett. “The Navy Concluded Transmedium Flying Submersibles Were Possible A Decade Ago.” The Drive, June 12, 2021. https://www.thedrive.com/the-war-zone/41045/the-navy-concluded-transmedium-flying-submersible-vehicles-were-possible-a-decade-ago.

18. Knuth, ““UAP Flight Characteristics: The Five Observables.” At 21min 27s.

19. Tingley, Brett. “Can The U.S. Military Make An Airplane Invisible To The Naked Eye?” The Drive, December 19, 2019. https://www.thedrive.com/the-war-zone/29543/the-visible-history-of-the-militarys-hunt-to-realize-an-invisible-aircraft.

20. Note: Many current and former members of the U.S. Defense Establishment have opined on the fact that the military will not conduct uncoordinated tests.

Former Deputy Assistant Secretary of Defense for Intelligence, Christopher Mellon, is quoted as saying: “We do not operate test aircraft in the vicinity of carrier battlegroups without some prior coordination. It would be completely uncharacteristic of the military to operate in such a strange haphazard manner. If that did happen, it would probably happen only once. Those people would be replaced in a hurry.” (History Channel: Unidentified Season 1 Episode 2).

Former Senior Chief, Kevin Day is also quoted as saying: “that’s just not how tests are done. Never in my career would you run a test on top of my test without telling me because of the safety of flight concerns. I mean, it’s illegal in terms of Navy doctrines and procedures… cause if I run into one, now we’re all in trouble. You could break aircraft and maybe someone dies, you know?” (Metabunk).