It will be no surprise to anyone who is even somewhat familiar with the UFO phenomena that there have been concerted efforts from various global militaries to conceal the truth of UFOs from the general public. There are arguably legitimate national security considerations of course, for example, if a top-secret aircraft was observed by civilians by accident, the responsible military would want to suppress the sighting. That may have been what happened in this 1948 incident in the skies of southwest Alabama.
At 2.45 AM on the morning of July 24th, 1948, two Atlanta-bound Eastern Airline pilots and the lone passenger spotted something crazy while flying in a twin-engine propeller plane at 5000 feet. You can read more about it here, but essentially, the folks saw what sounded light a blimp with observation decks and a jet on the back! 😂
https://www.history.com/news/ufo-chiles-whitted-soviet-spycraft-air-force-coverup
To be quite honest, I have read many reported sightings of far more impressive sounding propulsion systems than those reported by Clarence S. Chiles and co-pilot John B. Whitted. Flames coming out the back is hardly gravity manipulation!
I think this report was of a terrestrial technology, perhaps a top-secret Soviet spycraft. What do you think?