He worked as a private equity investor as of 2023[2] and was the Deputy Assistant Secretary of Defense for Intelligence in the Clinton and George W. Bush administrations and later for Security and Information Operations.

Following the transition, Mellon was appointed as the Coordinator for Advanced Concepts and Program Integration, Office of the Under Secretary of Defense for Policy, concentrating on encryption and information assurance issues.

In a 2016 interview with Leslie Kean published on the now-closed HuffPost Contributor Forum, Mellon stated: I highly doubt DoD or any other government agency is concealing UFO information.

Those efforts now appear to be hindered by new guidance that moves the classification yardsticks merely because some U.S. government officials dislike oversight and are uncomfortable sharing information.

"[9] Mellon worked with Leslie Kean in a UFO organization and is a shareholder and former advisor for the Blink 182 punk rocker Tom DeLonge's To The Stars Academy of Arts & Sciences.

[12] Mellon assisted in production and worked with former Pentagon Director of AATIP, Luis Elizondo as a cast member for the cable television network History that distributes the shows series Unidentified: Inside America's UFO Investigation.

[14] In the documentary, Mellon claims he met with an individual in the parking lot of the Pentagon and was handed a package containing three videos recorded by U.S. Navy pilots between 2004 and 2015.

[17] He also told media that he backed some of the claims made by David Grusch in a 2023 United States House Committee on Oversight and Accountability hearing, and said that "rightly or wrongly, a number of potential sources do not trust the leadership of the All-Domain Anomaly Resolution Office established by Congress.”[18]