The literal base of a UFO are copper plate capacitors (or equivalent material). The capacitor is flat relative to the ground. The negative plates must be on the bottom (relative to the ground). Starting at 1,000,000 volts (1MV), such a capacitor will start to float.
In "mainstream" physics, gravitational and electromagnetic attraction / repulsion obviously have "parallel" characteristics. The electric effects are (at least very roughly speaking) 1020 times more powerful. To break from the "mainstream," at least part of the "electric universe" theory is likely true. The electric universe says that "gravity" is electromagnetism, period. There is no separate gravity. "Gravity" exists because electrons can move slightly away from each other in a way that protons cannot. That is, the statistical cloud tends to move towards the surface of a planet. This causes the same effect on objects on the surface, with electrons very slightly clustering on the opposite side of the center of gravity. Thus, "gravity" is electromagnetic attraction caused by the fact that, statistically speaking, most of the electrons nearby you are very, very slightly closer to you than the protons, and your electrons are very, very slightly farther away than most protons. So, on net, your protons are pulled towards the center of the earth. Otherwise put, "gravity" is caused because atoms in a mass very slightly distort, and thus the net charge of atoms are not quite balanced.
Relative to slightly bent atoms, the UFOs negative plates are much closer to the earth than the positive plates. Thus, with just a bit more charge than the floating level, the UFO will leap into the sky at high acceleration. I've seen references to observed 30,000 feet per second and acceleration that would "crush" pilots--30g? 100g? Much higher?
The math is relatively easily crunchable. I think it would show that someone inside the UFO will accelerate with the craft, so he wouldn't feel 100g or any other acceleration. The force of acceleration comes from an essentially instant (for those purposes) electric effect. The whole craft and everything in it is having its gravity shoved. In a car, forward force goes from engine to tires to the frame to the seat to you. In a UFO, every atom is being accelerated at the same rate at the same time. The whole field is moving. I think that explains that part of it.
As for a lack of a sonic boom, I suspect it goes like this: air molecules have freedom to move such that air above the craft will be attracted to the positive plates--the positive plates are closer than the negative plates. Thus, relative to its size, the UFO attracts a large air mass above it. The math (modeling) would show that the molecules can move around such that they aren't forced against each other at supersonic speeds. The mass is big enough that the molecules slough (relatively gently push) away from each other rather than being forced together.
At least one of the US military's top-secret, special access, unacknowledged projects had mastered such "anti-gravity" by October, 1952. I believe that is the date that Dr. Steven Greer (MD) gives. Mark McCandlish, cited below, has quite a few stories that I find credible. He is one of dozens of similar witnesses. McCandlish's video is 20+ years old. He names names of people who may also have talked by now.
In roughly 2021, David Wilcock was talking about building something. He said he didn't care if he created the "Yugo" of UFOs that no one would buy. He just wanted to show that it could be done. Off hand, I can't find an update. Wilcock gets a lot of grief, but I have a number of reasons to think that he is very much for real. He's is a great thinker.
So when the Satanists are overthrown and we have "flying cars" in a few years, here are some musings on anti-collision, when there are tens of millions of UFOs just in the continental US.
My rough estimate is that given GPS, accelerometers, TCAS, ADS-B on steroids, and modern computing, current aircraft systems wouldn't need much adapting. ATC would be fully automated and partially decentralized.
I'm going to cut this short for now, but some thoughts: passive millimeter wave sensor / cameras, such as VuSystems. I've seen references to radars than can "see" sparrows at least mile away. We don't want to hit birds, of course. A few Canada geese will not force-land a UFO like it did Sully's plane, but we still don't want to crash into them. I've seen references that birds are considered a concern until 3,000 - 5,000 feet above ground.
Blueprint for a UFO - Mark McCandlish, US Air Force / Disclosure Project Witness Testimony Archive - Part of Dr. Steven Greer's (MD) project.
In terms of how it works, McCandlish starts off well and then makes it much more complicated than it is. Before 03:00 minutes, he's talking about copper plates. He gives people's names. I looked for one briefly and didn't find it, but Thomas Townsend Brown has an entry. McCandlish is talking about Brown before 04:00. Somewhat later, McCandlish is talking about zero-point energy and musing on a device that converts atomic spin into electric energy. I don't think it's nearly that complicated. The copper plates are enough of a basis.
Keep in mind that WikiPedia is great until it advises you to kill yourself with a lethal injection they call a "Covid" "vaccine." With that said, see the "Parallels between electrostatic and gravitational fields" and the Coulomb constant versus the gravitational constant.
This site has at least one helpful graphic on "Electric Gravity." It figures that the videos are gone. Damn YouTube.
As I'm writing this, this History Channel page on the "five observables" is broken. For reference, it involves former "AATIP Director Luis Elizondo" (US Department of ). Defense Advanced Aerospace Threat Identification Program). This also goes to the "Tic Tac" UFO video that came out in late 2017.