First was Maori Island incident. Three UFOs were flying over the lake, when one of the UFOs started sputtering hot molten metal (typical failure mode of UFOs, check Peter Sturrok's book for 4 more cases). Broken UFO started wobbling and descending, and than two other UFOs approached it and lifted it up. Clearly a case of an attractive force coming out of UFO's body.
For the second case I forgot almost all the details, except the main ones. An US family was traveling through outback with woods and mountains. It was a very long journey and it was late at night. At one point they stopped at a clearing just to stretch legs and so. Than 3 or 4 UFOs approached right above where their car was parked and all 3-4 UFOs started flying super fast in circle above the family. Again, purely mechanically, in this universe and the next, two forces must had been at play one outward centrifugal and another UFO propulsion related force acting attractively inwards.
Now this particular US case reveals to us even more about that misterious UFO attractive force. Because there were 3-4 UFOs, that attractive force can not be electric field force. Like electric charges repel, opposite charges attract. That means that attraction can only exist in a 2 body system, while in 3 or higher count charged body system polarities would need to switch back to repulsion. For example, if we have 2 UFOs one electrically charged + and other charged -, there would be a very strong attractive force between them and they would be able to perform all the above maneuvers. In a 3 body system, there would need to be say two + and one - charged UFOs, so two positive UFOs would repel each other. Appearance of repulsive force would add to centrifugal force and would make all above maneuvers impossible.
Studying cases like this helps us understand physics of UFOs. Unfortunately, while this behavior excludes electric force, it doesn't prove that the external attractive force between UFOs was gravitational. It is very typical of UFO landing sites that debris doesn't rise and attach itself to UFOs hull. But that could be just UFO propulsion management, because at a moment of landing, propulsion would be near zero.
Anyway, plenty food for thought.