Interesting! Most likely anti-gravity propulsion.
I knew a guy that built and sold the best gravity meters in the world for geology investigations. Years ago he was hired by the military to investigate the idea of “anti-gravity”. The military missiles were going off course by just a bit.
He said he could never measure any effects of anti-gravity. However, just the idea that the military would explore the idea makes me wonder that it might be real. Every other force in physics has an “opposite”.
An aside. Knew a guy that was a state wildlife officer. He went on a call with a biologist from the large University to collect a hair sample of a reported Bigfoot. Seemed odd that the state would send two professionals on a 6-hour round trip drive just to placate some farmer that thinks he saw something walk over his fence.