1. What is a UFO? In the landlord's question, UFO has been directly defaulted to aircraft. In fact, this understanding is inaccurate. UFO is originally a UFO, that is, a flying object unknown to the observer. For someone who has never seen stars, they are UFOs (don't laugh). Are they suspended by the earth's magnetic field? Obviously not. On the Internet, some people can confuse concepts and simply regard UFOs as alien aircraft. This logic is ridiculous.
The second problem is that alien spacecraft can't operate in this way.
My personal opinion is that it is possible in theory, but it is very difficult to operate. It is very difficult to rely on the geomagnetic field, and the magnetic force generated by the intensity of 0.005T can offset the gravity of the earth. Experiments have been done to determine the magnetic susceptibility of molecules. Under the condition of 0.5T, the magnetic induction force generated by ferrous sulfate heptahydrate containing five unpaired electrons is only about 0.2g, while the molecular weight of ferrous sulfate heptahydrate is about 25g, and the magnetic induction force is proportional to unpaired electrons. If such an airplane is to be built, it must be composed of hundreds of unpaired electrons. To reach this level, you need to give molecules very high energy. If I were an airplane designer, I wouldn't do such a design. If I want to have such energy to excite molecules, I might as well use it as a propeller. And this design is greatly influenced by the earth's magnetic field. If someone turns on the flashlight next to me, such a spaceship may crash (just electromagnetic waves).
So I can't deny the existence of such a design, because it is feasible in principle. However, it is indeed unwise, energy-consuming and greatly influenced by the outside world to make such involvement.