On a crystalline blue afternoon 20 years ago — Nov. 14, 2004 — four Navy pilots spotted a mysterious flying object 100 miles off the coast of San Diego. It looked like a Tic Tac candy, with no wings, no flight surfaces, no windows and no smoke trail. It moved like a high-speed ping pong ball at a speed later estimated to be 46,000 miles per hour.

The so-called “Tic Tac” incident eventually became one of the key episodes that led to an unexpected renaissance of serious interest in UFOs in 2017, and the pilots later appeared on “60 Minutes,” CNN and elsewhere to discuss their experience. The event is often cited by believers in UFOs, short for unidentified flying objects, as the most credible sighting ever.

The overall tone of the UFO discussion shifted abruptly in March, however, when the U.S. government’s All-Domain Anomaly Resolution Office released a highly skeptical report on the phenomenon. All-Domain Anomaly Resolution Office Director Sean Kirkpatrick argued that renewed UFO mania had been driven by a “whirlwind of tall tales, fabrication and secondhand or thirdhand retellings of the same.”

The report provided an important public service by authoritatively debunking some of the wilder claims in the UFO conversation, but it blinded many observers to the reality that the 63-page analysis did not attempt to solve the mystery of every single one of the claimed sightings, nor did it claim to do so. The most fascinating of these unsolved mysteries is the Tic Tac incident, which was accompanied by a well-known video. as well as unaccountable radar returns and visual sightings by members of the USS Nimitz Carrier Strike Group starting around Nov. 10, 2004.

While it’s true that there has never been one piece of concrete evidence that the Tic Tac craft came from outer space, it’s equally true that no hard evidence has emerged to support the idea that it was a weather balloon, an advanced Chinese drone, a sophisticated U.S. “spoofing” test of naval radar or an experimental U.S. test craft. Some of the alternative explanations, which have been explored in detail on both pro- and anti-UFO forums, are nearly as interesting as the alien spaceship hypothesis. A few raise important issues of national security and flight safety, even two decades later.

While the March All-Domain Anomaly Resolution Office report splashed cold water on UFO enthusiasts, it did confirm one of their pet theories: that many of history’s well-known UFO sightings were, in fact, secret government programs. As the report noted, many “sightings since the 1940s have represented misidentification of never-before-seen experimental and operational space, rocket, and air systems, including stealth technologies and the proliferation of drone platforms. Many of these technologies fit the description of a stereotypical Unidentified Flying Object.”

The All-Domain Anomaly Resolution Office lists 27 secret programs that could have been misinterpreted through the years as UFOs, including something called the “Flying Pancake” in 1942. It would not take an enormous leap of the imagination to believe that the Tic Tac belongs in this line of historic events.

But the All-Domain Anomaly Resolution Office paper makes no mention of any programs that could have caused the Nimitz observations — even though it cites examples of drones that were tested later. So the report, while demystifying the broader UFO conversation, actually ends up adding more mystery to the Tic Tac episode. If the U.S. government has secret information about this celebrated incident, one wonders, how and why has it remained hidden all of these years?

It would be a disservice to veterans like David Fravor who have risked ridicule (and worse) to testify before Congress and in other public forums about the extraordinary things they saw simply to abandon the search for the answer to the Nimitz case because some unrelated outlandish claims were taken too seriously by Congress and the media. This puzzling episode remains relevant, and it deserves continued investigation.

France is a former senior editor at BusinessWeek magazine who is the author of Nimitz Compendium, a comprehensive bibliography of the Tic Tac incident. He lives in Brooklyn.