Not all planes carry their passengers in parallel universes, it happens only sometimes.
The physics of quantum mechanics says that there are infinite parallel universes within an infinitely large multiverse, and in many of these universes a person made exactly like you are reading this same post right now.
But the world is not order and rationality, and in this great multiversal disorder the ripples of the infinite continuum temporal spaces are lacking.
So it happens that many times, when you get on an airplane and you pass the time lines of at least two real time zones (not the conventional ones that we decided), some of the passengers of the plane pass from one universe to another, without realize them naturally, and when they land they are convinced that they have reached their destination in their universe, while it is another self that has taken its place on the plane, in their universe, in their life. And they come down from the plane, they go to pick up the car of the other self in the parking lot, they go back home from the other self, they make love with the woman of the other self, while the other itself in their old universe behaves in the same way.
And perhaps only touches them the feeling of being elsewhere.
It can also happen that there is no exchange, that a person passes into another universe, but the other self does not arrive in his, because perhaps for a slight difference between the two universes his doppelganger or already dead, or maybe he had lost the plane that day, or the flight in the other universe was canceled, and so it happens that in a universe there are two duplicates, and in the other nobody, and many cases of people disappeared into thin air maybe you can explain just like that .
As this happens there is no paradox, and no breakdown of the continuum of time space that many science fiction writers fancy about the travel of time. Why in the end what will be some duplicates in the immensity of the multiverse?
There is only one world where you are not there, and another where there are two of you, as in many stories of the popular imagination and in that music video of a few years ago (of the song and the group I do not remember the names), where suddenly the protagonist discovers that another has taken his place at work, at home, until he also takes the car, the only thing that had remained.
