I just walked outside to flip some chicken on the grill and I could hear what sounded like extremely loud high altitude jet engines circling over the house. I went onto this website

https://www.flightradar24.com/

and there were no flights anywhere near my house at the time. So my question is: what kind of aircraft are these? What type of extremely high altitude jet doesn't show up on a flight tracker, and what are they doing circling the house in a rural area?