The U.S. Strategic Command’s Global Thunder exercise, which began on Oct. 22, is still underway. Flight data tracked B-52 bombers departing Minot Air Force Base in North Dakota and multiple E-6B Mercury aircraft operating over the U.S., the Daily Mail reported on Wednesday. The E-6B is the Navy’s nuclear command and control aircraft from which launch orders can be transmitted to bombers, submarines and ICBMs. Global Thunder is expected to run about 10 days.

Aviation notices outlined temporary airspace reservations over parts of the Atlantic, Pacific and Florida potentially linked to Global Thunder, with one explicitly naming the nuclear exercise. Officials stressed that Global Thunder is an annual exercise and is not a response to any country or current world events.

Flight-tracking data also showed B-52 bombers heading north from the Minot area in North Dakota into Canada, while others followed looping routes over Louisiana and Mississippi.