investigators wrote:

What do these people have in common?

Paul Hill, NASA scientist, Professor of Aeronautics, Polytechnic College of
Engineering, Oakland, California; also employed at Langley Research Center.

John E. Mack, M.D. Professor of psychiatry at Harvard Medical School.

Colonel Philip J. Corso (Ret.)  Member of President Eisenhower's National
Security Council, former head of the Foreign Technology Desk at the U.S.
Army's Research & Development department.

J. Allen Hynek, Chairman Dept. of Astronomy Northwestern University. Served
as official astronomical consultant to the U.S. Air Force's Project Blue
Book, and was Professor of Astronomy at Ohio State University.

Bruce Maccabee, Ph.D. Physicist employed by U.S. Navy.

David M. Jacobs, Ph.D.  Associate Professor of History at Temple University.

Leslie Phillips.

Michael Jackson.

The late Professor Jimmy Edwards.

Here's a clue:  W-----!