Here's a better article on the plane … and it gets more interesting
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.
– More on the E-6B –
The Boeing model is part of the Navy's TACAMO mission, which stands for Take Charge And Move Out. The Navy basically uses the plane as a mobile command center that will be functional and reliable in times of crisis.
Sixteen units were created for the Navy, and they operate out of Oklahoma, frequently using the flight call letters of IRON99.
https://www.thedenverchannel.com/news/local-news/navy-identifies-mystery-plane-over-denver-its-mission-still-a-secret