This can't be done without hacking, soo... where's the glitch? I would call it hack not glitch...

hacks? how is that a hack?

if that's called hacking than i am pretty sure about 99.9999999% peoples can hack the game
and you are in the 0.0000001% that do not know how to edit the perk and change the speed to max.

Tell me, how can you fly without hacking?

holly fuck /facepalm
try this
1.go to private match
2.change game mode to any
3.go to edit game options.
4.go to class editor and choose custom classes.
5.disable and make any classes u want make sure u have lightweight pro and marathon pro on.(to get pro press square/x when on the perks)
8.go to movement speed and sprint speed and choose fast or very fast.
9.go to perk editor go to pro perks then choose pro perk 1 and make lightweight x2 and do what ever you want for perk 2

easy as that and you are talking about flying is a guy jumps with super speed it is going to be a super jump
/facepalm