This is a really cool invention, and I think it would be a lot of fun to use. But it's not the first personal flying device, and fuel considerations have been an obstacle to many of those.
https://en.wikipedia.org/wiki/Jet_pack
"their uses are much more limited than their fictional counterparts because of the challenges of Earth's atmosphere, gravity, low energy density of available fuels, and the human body not being suited to fly, and they are principally used for stunts"
The "low energy density of available fuels" is a concern for this device too: note that the prototype required refueling in order to cross the English Channel. Having to carry your own fuel is a big limitation for flying machines.