The Pentagon is investigating a rising number of cases involving unidentified aircraft, the head of the agency’s effort told senators on Wednesday, and is now tracking some 650 incidents.

Two new videos were released at the rare open congressional hearing on Unexplained Anomalous Phenomena, or UAPs as the Pentagon calls them, to highlight how the recently established All-domain Anomaly Resolution Office (AARO) can explain some incidents but not others.

Sean Kirkpatrick, director of the All-Domain Anomaly Resolution Office, also looked to tamp down some of the out-of-this-world speculation about what’s behind the sightings, telling senators that his shop has found no evidence of alien activity.

Three members of the Senate Armed Services committee heard testimony from Sean Kirkpatrick, director of the All-domain Anomaly Resolution Office. AARO was formed last year by the Pentagon to help study unidentified aerial phenomena, or UAP, the government’s preferred term for mysterious objects seen in the sky.

“This is a hunt mission for what [somebody might] be doing in our backyard that we don’t know about,” said Kirkpatrick, who added that the goal was to set a standard across the entire Department of Defense for this type of investigation.

Kirkpatrick outlined to lawmakers how his office is helping the Pentagon and intelligence community to identify emerging foreign technologies, including his role in helping to identify the high-altitude surveillance balloon from China that flew over US airspace in February.

He played video from two of cases that had been declassified, one that had been resolved and the other unresolved.

The first video showed a small orb that flew through the camera screen of an MQ-9 drone in the Middle East in 2022. The drone’s camera followed the object as it moved through the sky, coming in and out of the screen.

Kirkpatrick explained that this case was unresolved because there was no other evidence beyond the video. “It is going to be virtually impossible to fully identify that, just based off of that video,” he said, adding that the hope was as more data was gathered on these episodes, patterns could emerge to help explain the unresolved cases.

In the second video from South Asia earlier this year, an object flew by two MQ-9 drones, including one that captured video appearing to have a propulsion trail behind it, which Kirkpatrick said was initially believed to be “truly anomalous.”

But he said after they pulled apart the video frame by frame, his office determined that it was a “shadow image.”

“This is in the infrared, this is the heat signature off the engines in a commuter aircraft that happened to be flying in the vicinity of where those two MQ9s were at,” he said.

Kirkpatrick did say there was a plan in place should evidence of an alien technology arise, stating, “In the event sufficient scientific data were ever obtained that a UAP encountered can only be explained by extraterrestrial origin, we are committed to working with our interagency partners at NASA to appropriately inform U.S. government’s leadership of its findings.”

Kirkpatrick showed a chart with reporting trends of anomalies from 1996 to 2023, which found that most sightings were of a round object, one to four meters in length and typically white, silver or translucent, at an altitude between 10,000 and 30,000 feet with no thermal exhaust detected.

The sightings were clustered along the East and West coasts of the United States, in the Middle East and near Japan and the Korean peninsula.

Concerns over incursions into U.S. airspace by unknown objects have gripped Washington in recent years, and Kirkpatrick’s office was established last July to spearhead the analysis of sightings. But he also sought to temper assertions that UFOs have a non-worldly explanation.

Kirkpatrick, however, made waves with a draft paper he co-authored with Harvard professor Avi Loeb last month that presents a theory that some recent objects that appear to defy physics could be “probes” from an extraterrestrial mothership.

No senators asked Kirkpatrick about the paper at Wednesday’s hearing, however.