Sean Kirkpatrick will retire next month.
The chief of the Pentagon's UFO investigation division will step down in December, the Department of Defence said. Sean Kirkpatrick, Director of the All-Domain Anomaly Resolution Office (AARO), announced his retirement after a 27-year career in the department and the United States Intelligence Community. He announced his plans after leading the department for 18 months. He stated that sightings of objects flying in the sky over the US are either aliens or technology of rival nations.
"I'm ready to move on. I have accomplished everything I said I was going to do," Mr Kirkpatrick told Politico. He said that he still wants to finish "wrapping up the first volume of a historical review of the unidentified anomalous phenomena issue", before leaving office.
Mr Kirkpatrick warned of the presence of UFOs after studying more than 800 instances during his tenure as director, and while there has yet to be any firm evidence of aliens, he felt the alternative was much more frightening. "If we don't prove it's aliens, then what we're finding is evidence of other people doing stuff in our backyard. And that's not good," he added.
The announcement comes barely a week after Mr Kirkpatrick stated that AARO will create a reporting mechanism for current and former US federal employees and contractors who witnessed US government-related actions involving unidentified anomalous phenomena.
The system was established just months after former US intelligence official David Grusch testified before Congress that the Pentagon had recovered wrecked vehicles of unknown origin containing "non-human biologics." Mr Kirkpatrick claimed that he has frequently requested Mr Grusch for additional evidence to back up his assertions and has received no response. The Pentagon has insisted that it was unaware of any reverse engineering efforts, craft recovery, or discoveries pertaining to "non-human biologics."
The Department of Defence praised Kirkpatrick's leadership and credited him for building the organisation's first website that was accessible to the public, increasing the AARO's level of transparency. "His commitment to transparency with the United States Congress and the American public on UAP (Unidentified Aerial Phenomena) leaves a legacy the department will carry forward as AARO continues its mission. Our department is stronger and better prepared for future scientific and national security challenges because of Sean's distinguished service to our country," a statement said.
Tim Phillips will serve as the deputy director of AARO until the Pentagon appoints a permanent replacement, according to the statement from the Defence Department.