The title of the dance song "Like a G6" by Far East Movement. It refers to a Gulfstream G650 airplane.
When something is "fly like a G6", they are stating that it's quite awesome.
Poppin bottles in the ice, like a blizzard
When we drink we do it right gettin slizzard
Sippin sizzurp in my ride, like Three 6
Now I’m feelin so fly like a G6