UFO researcher Shepherd Johnson of Virginia was researching Carl Sagan's papers at the Library of Congress in Washington, DC.
He found a fascinating attempt by Laurance Rockefeller to draw Sagan into his pro-UFO advocacy (Johnson posted this to the Facebook group UFO Updates). The American billionaire Laurance Rockefeller (1910 - 2004) was the son of John D. Rockefeller, Jr., and the brother of Nelson Rockefeller. His UFO "disclosure initiative" is well-known in UFO circles. According to Wikipedia,
In 1993, along with his niece, Anne Bartley, the stepdaughter of Winthrop Rockefeller and the then-president of the Rockefeller Family Fund, he established the UFO Disclosure Initiative to the Clinton White House. They asked for all UFO information held by the government, including from the CIA and the US Air Force, to be declassified and released to the public. The first and most important test case where declassification had to apply, according to Rockefeller, was the Roswell UFO incident. In September 1994, the Air Force categorically denied the incident was UFO-related. Rockefeller briefed Clinton on the results of his initiative in 1995. Clinton did produce an Executive Order in late 1994 to declassify numerous documents in the National Archives, but this did not specifically refer to UFO-related files.
In addition to funding UFO research, Laurance Rockefeller also funded research into Crop Circles, and ESP.
SETI has no data, says Rockefeller's argument, but UFOlogy does. Sagan's reply was brief and pointed:
"A million reports that the Earth is flat has no veridical value on the shape of the Earth." - Carl Sagan.