The U.S. government can't explain 143 of the 144 cases of unidentified flying objects reported by military planes, according to a highly anticipated intelligence report released Friday.
That report, released by the Office of the Director of National Intelligence, was meant to shed light on the mystery of those dozens of flying objects, spotted from 2004 to 2021, but instead said it didn't have adequate data to put all but one of them into a category.
That one UAP — shorthand for "unidentified aerial phenomena" — was a large, deflating balloon, the report said.
"The others remain unexplained," the report, which was required by Congress, added.
While the report explicitly stated that "unusual" activity had been reported on multiple occasions, it also did not rule out that those incidents were the result of errors or "spoofing."
"In a limited number of incidents, UAP reportedly appeared to exhibit unusual flight characteristics. These observations could be the result of sensor errors, spoofing, or observer misperception and require additional rigorous analysis," the report said.
The report does not mention aliens or even vaguely hint at an extraterrestrial explanation for the reported sightings, but makes clear that much of the phenomena may be beyond the existing means the government has to identify such objects.
A senior U.S. government official said ahead of the report's release Friday that, "We have no clear indications that there is any nonterrestrial explanation for them — but we will go wherever the data takes us."
The official added: “We do not have any data that indicates that any of these unidentified air phenomena are part of a foreign collection program nor do we have any data that is indicative of a major technological advancement by a potential adversary."
Last month, speaking about the upcoming report, officials told NBC News the government had not ruled out the possibility that the flying objects seen by U.S. military planes were highly advanced aircraft developed by other nations. These officials also said that the objects did not appear to be evidence of secret U.S. technology, but didn't definitively rule that out, either.
However, the report — the result of a provision in the $2.3 trillion coronavirus relief and appropriations bill that former President Donald Trump signed last year — said these "unidentified aerial phenomena" represented safety of flight issues and potential operational security issues. Parts of the report remained classified.
“There is a wide, wide range of phenomena that we observe that are ultimately put into the UAP category. There is not one single explanation for UAP, it’s rather a series of things," the senior U.S. official said Friday.
The Department of Defense established the Unidentified Aerial Phenomena Task Force in August to investigate and "gain insight" into the "nature and origins" of unidentified flying objects. Earlier that year, the Department of Defense declassified three videos taken by Navy pilots — one from 2004 and two from 2015 — that showed mysterious objects flying at high speeds across the sky.
"The aerial phenomena observed in the videos remain characterized as 'unidentified,'" Pentagon officials said in a statement at the time.
The three videos had leaked years earlier, but Pentagon officials said they declassified the footage to "clear up any misconceptions by the public on whether or not the footage that has been circulating was real, or whether or not there is more to the videos."
No additional incidents or videos were released Friday as part of the report.
According to the report, there were 18 incidents reported in which the UAPs that were seen featured some sort of "unusual movement patterns or flight characteristics" including propulsion or other technology that wasn't evident and that could be advanced. Eleven of the incidents reported were near misses with military planes, the report said.
"Some UAP appeared to remain stationary in winds aloft, move against the wind, maneuver abruptly, or move at considerable speed, without discernable means of propulsion," the report said, in describing those incidents. "In a small number of cases, military aircraft systems processed radio frequency (RF) energy associated with UAP sightings," the report added.
The report also said "there was some clustering of UAP observations regarding shape, size, and, particularly, propulsion" and that "UAP sightings also tended to cluster around U.S. training and testing grounds."
The report, however, concluded that "this may result from a collection bias as a result of focused attention, greater numbers of latest-generation sensors operating in those areas, unit expectations, and guidance to report anomalies."
All videos of the incidents that have so far been released remain unexplained, the report said.
The report noted that the limited amount of anecdotal data — as opposed to scientific data — and inconsistencies in reporting due to the lack of a standardized system make evaluating UFOs a challenge.
"The limited amount of high-quality reporting on unidentified aerial phenomena (UAP) hampers our ability to draw firm conclusions about the nature or intent of UAP. The Unidentified Aerial Phenomena Task Force (UAPTF) considered a range of information on UAP described in U.S. military and IC (Intelligence Community) reporting, but because the reporting lacked sufficient specificity, ultimately recognized that a unique, tailored reporting process was required to provide sufficient data for analysis of UAP events," the report said.
“We quite frankly have a bit of work yet to do in order to truly assess and address the threat posed by UAP," the senior U.S official said Friday. “Not all UAP are the same thing.”
The Pentagon, the report said, would prefer to rely on a scientific and data-driven approach to collecting information on the UAP, instead of the anecdotal observations reported by military planes.
To that end, the Office of the Director of National Intelligence and the Pentagon are making efforts to create a new collection strategy to standardize data reporting on UFOs, according to the report. The agencies said they will update Congress on their progress within the next 90 days, the report said.
In a statement after the report's release, Pentagon Press Secretary John Kirby said the intelligence office had been ordered to develop a plan to formalize that mission.
Lawmakers from both parties demanded the government do more to investigate.
“The United States must be able to understand and mitigate threats to our pilots, whether they’re from drones or weather balloons or adversary intelligence capabilities,” said Senate Intelligence Committee Chairman Sen. Mark Warner, D-Va. “Today’s rather inconclusive report only marks the beginning of efforts to understand and illuminate what is causing these risks to aviation in many areas around the country and the world.”
Sen. Marco Rubio, the top Republican on that committee, added: “This report is an important first step in cataloging these incidents, but it is just a first step.”
“The Defense Department and Intelligence Community have a lot of work to do before we can actually understand whether these aerial threats present a serious national security concern,” added Rubio, who pushed the government to conduct the UFO report.
House Intelligence Committee Chairman Rep. Adam Schiff, D-Calif., said, “We should approach these questions without preconceptions to encourage a thorough, systematized analysis of the potential national security and flight safety risks posed by unidentified aerial phenomena, whether they are the result of a foreign adversary, atmospheric or other aerial phenomena, space debris, or something else entirely."
This article was originally published on NBCNews.com.