Story highlights Elizondo said he stepped down from the Department of Defense in October

He said some aircraft they looked into were "seemingly defying the laws of aerodynamics"

(CNN) A former Pentagon official who led a recently revealed government program to research potential UFOs said Monday evening that he believes there is evidence of alien life reaching Earth.

"My personal belief is that there is very compelling evidence that we may not be alone," Luis Elizondo said in an interview on CNN's "Erin Burnett OutFront."

A pair of news reports in The New York Times and Politico over the weekend said the effort, the Advanced Aviation Threat Identification Program, was begun largely at the behest of then-Senate Majority Leader Harry Reid, D-Nevada, who helped shore up funding for it after speaking to a friend and political donor who owns an aerospace company and has said he believes in the existence of aliens.

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Elizondo told The New York Times he resigned from the Department of Defense in October in protest over what he called excessive secrecy surrounding the program and internal opposition to it after funding for the effort ended in 2012.

Elizondo said Monday that he could not speak on behalf of the government, but he strongly implied there was evidence that stopped him from ruling out the possibility that alien aircraft visited Earth.

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