What makes them fly?

[itachiXnagato]

How come its only the hidden stone shinobi that can fly?

 

[gordo1]

They make tiny little rocks in make them hover and stand on them. /sarcasm

I have no idea, good question

 

[Elio]

They can dramatically increase or decrease weights of objects/beings.

 

[~Dream~]

They is only one alive. Which is Oonoki.

 

[Houssem Uchiha]

Only Onoki does it, but he can make others fly simply by controlling his and their weight

 

[icedonkey]

I guess it has something to do with decreasing their weight.
A ability of Oonoki's.
How exactly I do not know.

 

[The Scion of Hentai]

I guess it must be some sort of specialized jutsu relative only to the Hidden Stone. Its not a kekkei genkai or anything as Mu (Second Tsuchikage) and the First Tsuchikage have also been shown and said to be able to pull off the jutsu.
P.S It's pretty dang awesome. Flight, super-speed, super-strength and jutsu, these guys are one latex costume and cape away from being Superman.

 

[GreenV]

They can decrease their weight.

They can also make anything they touch weightless.