A long-awaited U.S. government report on UFOs released Friday makes at least one thing clear: The truth is still out there.

Investigators did not find extraterrestrial links in reviewing 144 sightings of aircraft or other devices apparently flying at mysterious speeds or trajectories. But they drew few other conclusions and instead highlighted the need for better data collection about what’s increasingly seen by Democrats and Republicans as a national security concern. In all but one of the sightings investigated, there was too little information for investigators to even broadly characterize the nature of the incident.

There were 18 cases in which witnesses saw “unusual” patterns of movement or flight characteristics, the report said, adding that more analysis was needed to determine if those sightings represented “breakthrough” technology.

Long the domain of science fiction and so-called ufologists, the subject of UFOs has in recent years drawn serious study from the Pentagon and intelligence agencies. The prospect of an adversary spying with unknown technology has alarmed lawmakers in both parties.

Congress last year required the creation of the report delivered Friday. While its lack of conclusions has already been made public, the report still represents a milestone in the study of the issue.

U.S. officials who briefed reporters on condition of anonymity said there were “no clear indications” that the sightings could be linked to alien life. There is also no definitive linkage of sightings to potentially unknown technology of an adversary like Russia or China.

“It’s clear that we need to improve our capacity to further analyze remaining UAP observations, even as we accept that there are some limits to our capacity to characterize and understand some of the observations that we have,” one official said.

The report was published online and delivered to the House and Senate intelligence committees with a classified annex. Lawmakers were given a briefing last week on the investigation. One person who attended the classified briefing and spoke on condition of anonymity said lawmakers were given little information beyond what’s publicly available and that the only videos shown had already been made public.

The report lists five potential categories of what the government calls “unidentified aerial phenomena,” including the possibility of foreign adversaries flying unknown technology to events occurring naturally in the atmosphere.

But only one was categorized as “airborne clutter” and believed to be a large, deflating balloon. The rest are uncategorized due to lack of information. That includes three instances of potential sightings captured on videos that were declassified and released in recent years.

“It has become increasingly clear that unidentified aerial phenomena are not a rare occurrence and our government needs a unified way to gather, analyze, and contextualize these reports,” House Intelligence Committee Chairman Adam Schiff said in a statement.

“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,” the L.A. area congressmember added.

The Department of Defense will over the next three months develop a new strategy for collecting and tracking information on potential sightings. Part of the data collection effort is destigmatizing UAPs and pushing pilots to report what they see, even when what they see is implausible.

“A big problem around UAPs has been the cultural stigma,” said U.S. Rep. Andre Carson, an Indiana Democrat and member of the House intelligence committee, in an interview last week. “It has largely been relegated to science fiction.”

U.S. Sen. Marco Rubio, who as the top Republican on the Senate Intelligence Committee has long pushed for more disclosure about UAPs, called the report “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,” Rubio said in a statement.