The Pentagon has a specific technical framework for the most baffling UAP cases in its 2,000-file archive - five physics-defying behaviors identified from real pilot testimony and sensor data that mark an object as 'unresolved.'
In 2023, the head of the Pentagon’s UFO investigation office briefed the Senate Armed Services Committee on a property shared by some of the most baffling cases in the office’s archive. The objects being tracked were typically small - one to four meters across - white or translucent, operating between 10,000 and 30,000 feet. They could hover. They could accelerate to Mach 2. And they left behind no thermal exhaust.
That last detail is the physics puzzle. At Mach 2 - roughly 1,500 miles per hour, twice the speed of sound - air compression and friction generate significant heat. Every known high-speed aircraft, including classified military ones, leaves an infrared trail that can be detected from miles away. An object moving at Mach 2 without any heat signature is not something current propulsion science can produce.
The All-domain Anomaly Resolution Office (AARO) director was not speculating. He was summarizing data from the office’s own case files. And the thermal exhaust problem was just one entry in a longer list.
Investigators who analyzed years of classified UAP data identified five specific “observables” - categories of flight behavior that appear repeatedly in the most anomalous cases and cannot be matched to any known technology. Former Pentagon AATIP (Advanced Aerospace Threat Identification Program) investigators brought this framework to public attention when classified UAP footage was first disclosed in late 2017. The five observables have since been referenced in official government briefings and congressional hearings.
Anti-gravity lift. The object flies without wings, rotors, jet exhaust, or any visible means of generating lift. In multiple documented encounters, pilots described smooth, featureless craft hovering silently, without any of the sound or turbulence associated with known aircraft or drones. No thrust vector, no downdraft.
Instantaneous acceleration. The object reaches extreme speeds in a fraction of a second. The forces implied by some observed accelerations - based on sensor data and pilot accounts - have been estimated at hundreds of G-forces. For reference, a trained fighter pilot can sustain roughly 9 Gs before losing consciousness. The 2004 USS Nimitz “Tic-Tac” encounter, the most thoroughly documented UAP case in the public record, involved an object that appeared to reverse direction and accelerate beyond sensor range in less than two seconds.
Hypersonic velocity without signatures. This is the thermal exhaust problem. But it extends further. At supersonic speeds, aircraft generate a pressure wave - the sonic boom that follows a fast jet. Objects in UAP reports routinely exceed the speed of sound without producing one. No exhaust plume, no ionized atmospheric trail, no visible shockwave: none of the physical byproducts that moving fast through air should produce.
Low observability. The object is difficult to detect on radar despite being visually present. In documented cases, pilots have seen objects clearly while radar showed nothing. In others, radar tracked something the crew could not see. A subset of AARO case files describes what appears to be active interference with radar systems - the object disrupts sensor readings while remaining visible to observers nearby.
Transmedium travel. The object moves between different physical environments - air and water, or air and near-space - without slowing down or changing apparent form. Sensor data associated with the USS Theodore Roosevelt carrier group, which operated off the Atlantic coast in 2014 and 2015, reportedly tracked objects making high-speed transitions into and out of the ocean.
The five observables function as a diagnostic tool. When AARO reviews a reported encounter, analysts test it against conventional explanations: commercial drones, foreign military aircraft, weather balloons, atmospheric phenomena, sensor artifacts. The vast majority of reports resolve at this step - the object turns out to be something identifiable once the data is checked.
The cases that do not resolve are the ones where the observed behavior, particularly properties from the list above, cannot be matched to any known manufactured object, atmospheric phenomenon, or capability attributed to any known adversary. AARO director Jon Kosloski reported in June 2026 that approximately 40% of the office’s more than 2,000 active cases currently carry that “unresolved” label.
That amounts to roughly 800 open files in which U.S. government analysts, after running their full investigative process, have no conventional explanation.
AARO’s own case documentation, included in the classified and partially declassified material released through the PURSUE program in 2026, describes a specific “target package” - a profile of the most common characteristics seen across unresolved cases. Size: one to four meters. Color: white, silver, or translucent. Altitude: 10,000 to 30,000 feet. Speed: stationary to Mach 2. Thermal exhaust: none detected. The office uses this profile as an active search template.
“Unresolved” is not a conclusion. AARO has been explicit and consistent on this point: none of the cases reviewed to date have produced physical evidence of extraterrestrial technology. The 2024 AARO historical review found no verifiable evidence the U.S. government possesses non-human-origin craft.
Sensor systems have well-documented limitations - radar coverage gaps, infrared calibration drift, data-link latency that can make a fast-moving object appear to jump rather than travel smoothly. Pilot perceptions under the stress of a high-speed intercept are subject to errors in range and velocity estimation. Some behavior that appears instantaneous to a human observer may be an artifact of how sensor sweeps are timestamped and stitched together.
What the five observables framework offers is not an answer. It is a precise description of what the unanswered questions look like after the standard answers have been ruled out. The Pentagon has been, in the words of former AARO director Sean Kirkpatrick, “out hunting” for objects that match the profile. Three tranches of PURSUE records released through mid-2026 suggest it is still finding them.
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