At first, I kind of thought that the ability to fly in Yu Yu Hakusho would only be possessed by demons such as Jin, you know, people who are able to manipulate wind.
However, in the Demon World Tournament, not only did I find out that flying isn't only a Wind Master's power, but there are others who can do it better than them! Souketsu, one of Raizen's old friends beat Jin in a "race" to the sky. And not only that, Jin did not even know that Souketsu had even taken flight! "That's the Wind Manipulator's tragic flaw. You cannot exceed the speed of the wind itself."
So I suppose that means that Jin isn't able to fly faster than the speed of the wind.
But, that leaves the question, how did Souketsu fly? And not only that, Shuu, another of Raizen's friends flew as well! Neither Shu or Souketsu looked as if they were demons with flight as a native ability, so I am going out on a limb and saying that flying can be leanred as an additional skill.
So, if Souketsu and Shu can do it, who's to say that Enki can't? Or Natsume? Or Kujou? Or the rest of Raizen's friends? We never get to see it, but I think there is a good possibility they can as well.