How do you think they'll work? If they're using jets, then they are going to need a VERY large amount of fuel if you want to go very far. If they're using fans, THOSE FANS ARE GONNA HAVE TO GO SUPER FAST!! which will take either a very powerful battery (plausible, with some Xenon compound which holds a very large charge). If it's some form of Anti-Grav, then lol, that shit is so far away.
At least ten years.