The US has a truly incredible rule -- 14 CFR Part 103, usually shortened to Part 103 -- that basically deregulates ultralight aircraft, other than restricting their airspace usage. The logic behind this rule is that it defines ultralights tightly enough (low weight, low kinetic energy, restricted use over populated areas) that you're probably only going to kill yourself if something goes wrong; and what can be more American than allowing that?

The main defining features of a Part 103 ultralight are empty weight (< 254 lbs, including battery but not including up to 5 gallons of fuel, and with additional credits for parachutes and floats), minimum flight speed (stall speed for a fixed wing aircraft) of <= 24 kts or calculated equivalent (see AC 103-7), and maximum horizontal flight speed of 55 kts (with electronic or other artificial restriction of speed being acceptable).

Many of the "jetpacks" and other ultralight VTOL ideas being explored right now easily fit within Part 103, so in the US these certainly can fly, at least for very limited recreational usage.

> you're probably only going to kill yourself if something goes wrong; and what can be more American than allowing that?

I don't think the reason for this deregulation is that the FAA doesn't care if you only kill yourself, but rather that the number of people interested in doing this is and was in practice incredibly small. Yes, anyone can go buy a paramotor for $10,000 and probably figure out how to operate it just well enough to be able to kill themselves, but in practice this is extremely rare.

You can be sure that if it somehow became wildly popular for people to buy these things and it was causing lots of problems, the regulations would change. The exact thing happened with the massive popularity of "drones," which were similarly deregulated because the usage of RC aircraft had also been limited to a small number of RC clubs around the country.

§ 103.15 Operations over congested areas.

No person may operate an ultralight vehicle over any congested area of a city, town, or settlement, or over any open air assembly of persons.

> including up to 5 gallons of fuel

That's enough to reach critical mass of many fissile elements. I wonder if it would be possible to build a miniature nuclear rocket with enough thrust to lift a human. The weight budget probably isn't enough to include enough shielding.

You would need to get regulatory approval to operate the reactor.

The hand wringers and spineless politicians looking to score a few cheap brownie points for advancing "safety" will go after jet-packs if they ever become seriously viable. Look at all the hand wringing over the unwashed masses getting their hands on cheap and fast ebikes. Right now nobody cares because they're just rare toys for rich people.

No-one's freaking out about those parachutes with a lawnmower engine & seat attached, and those have been around for many years and can be seen flying all over (at least) the rural Midwest.

Now, flying them over other people's property or over a city is, and should be, another story.

> Now, flying them over other people's property or over a city is, and should be, another story.

It's not "one of the most dreamed of forms of flight – jetpacks" if you can't fly around town.

Right, and that’s probably never going to happen because of noise issues alone.

Jetpacks are a little bit like the Elon Musk tunnel digging startup: it is something you dream about when stuck in traffic during your commute.

Sort of, but a tunnel network of that type is never going to be able to handle many users, no matter how good the design gets, while improved and safe jetpacks probably could replace most of the cars on the road.

I doubt it, for basically the same reason that electric bicycles are not going to replace most of the cars. They might be great, but are not very nice for long commutes in poor weather (while wearing fancy suits or dresses/skirts).

For jetpacks there is an additional huge problem with safety flying over inhabited areas. Unless the jetpacks are meticulously maintained and inspected, we would see people falling out of the sky on the daily. Taking the maintenance state of most cars as an example, it seems safe to state that it would be infeasible to expect the general population to keep their jetpacks in an acceptable state.

Electric bikes are also significantly slower than cars and expose you to a lot of ground-based hazards, even on the days with the best weather.

It's honestly gone better than I expected as someone who built their first ebike back in 2006.

"not sure jetpacks are going to fly." I lol'd