Our readers are plenty interested in unidentified flying objects. We know that from the huge response to our front-page Sunday article (published online just after noon on Saturday) revealing a secret Pentagon program to investigate U.F.O.s. The piece, by the Pentagon correspondent Helene Cooper, the author Leslie Kean and myself — a contributor to The Times after a 45-year staff career — has dominated the most emailed and most viewed lists since.

So how does a story on U.F.O.s get into The New York Times? Not easily, and only after a great deal of vetting, I assure you.

The journey began two and a half months ago with a tip to Leslie, who has long reported on U.F.O.s and published a 2010 New York Times best seller, “UFOs: Generals, Pilots and Government Officials Go on the Record.” At a confidential meeting Oct. 4 in a Pentagon City hotel with several present and former intelligence officials and a defense contractor, she met Luis Elizondo, the director of a Pentagon program she had never heard of: the Advanced Aerospace Threat Identification Program.

She learned it was a secret effort, funded at the initiative of the then Senate majority leader, Harry Reid, starting in 2007, to investigate aerial threats including what the military preferred to call “unidentified aerial phenomena” or just “objects.” This was big news because the United States military had announced as far back as 1969 that U.F.O.s were not worth studying. Leslie also learned that Mr. Elizondo had just resigned to protest what he characterized as excessive secrecy and internal opposition — the reason for the meeting.