UPDATE: Navy identifies mystery plane over Denver; Its mission still top secret...
A day later -- after the plane landed -- Navy officials responded to comment on the flight, confirming it did hang over Denver for roughly an hour in a holding pattern.
Lt. Leslie Hubbell, who is the assistant public affairs officer for Commander Naval Air Forces, confirmed IRON99's identity is a Navy E-6B Mercury, created by Boeing at a cost of $141.7 million per unit.
The unit's overall mission is classified, Hubbell said, but did confirm the mission of the plane's class.
"The overall mission of the E-6B is command, control and communications abilities to direct and employ strategic resources," Hubbell said.
In laymen's terms, the planes are able to launch nuclear missiles and communicate with diverse assets, including nuclear submarines.
According to the Navy's website, the E-6B is a high-tech and large plane, each of which is equipped with an airborne launch control system that can reliably launch intercontinental ballistic missiles (ICBMs).
As to what the incredible weapon was doing above the Denver skyline -- Hubbell said it was halted by the FAA when traveling from its forwarding base in California back to Tinker Air Force Base, where the planes are serviced and housed.
The plane's forwarding location is Travis Air Force Base in Northern California, which declined to admit the plane departed from the base earlier Wednesday morning when asked by Denver7.
Travis Air Force Base officials weren't alone, the FAA said it had no contact with the plane Wednesday despite Hubbell's statement that the FAA told the plane to hold over Denver.
Although the Navy said the plane simply was flying from its forwarding base back to home base, a high-ranking federal official who wasn't authorized to speak on the matter said the plane was involved in a classified training mission organized by the Department of Defense.
The training mission reportedly centered around electronic surveillance and involved several agencies which aren't likely to comment on the mission, the source said.
The source said the mission wasn't out of the ordinary despite its size, noting the public isn't usually aware of such training missions.
It's not known if the mission had anything to do with a Denver-area mission to evaluate drone detection near the Denver International Airport. The FAA announced it would conduct work with the help of the Department of Defense, the Department of Homeland Security and more to help learn what technologies can aid in safely detecting drone activity near airports.
Members of the public got a rare glimpse of a powerful military tool, potentially on a training mission thanks to the clear skies over Denver, but it is no longer a mystery.
Mystery flight circles over Denver; Officials have few answers...
Thousands saw a plane circling the Denver metro area late Wednesday morning, questioning where it may have come from and what it may be doing. Officials at a host of federal organizations had few answers.
Denver7 began tracking a flight named IRON99 as it traversed from California over the pacific. It traveled over the Rocky Mountains and eventually over the Denver metro area.
Its arrival over the Denver metro is what prompted questions from a host of locals who saw it circling, questioning what it might have been doing.
Visually, the plane circled in a racetrack-style oval shape over the City of Denver at roughly 32,000 feet several times.
After spending time making its loops, the aircraft then took off in a direct path to Oklahoma, without any record of stopping.
Denver7 reached out to a host of official sources in an attempt to learn more about the flight, but sources couldn't confirm many details at all.