Within any single country with a population of at least 10 million people.
"Flying cars" are herein defined as vehicles which are legal to operate on the roads of the country, and which also can be operated as legal aircraft in that same country.
The two operations modes are not required to be covered by the same license. No type certificate, production certificate, or equivalent is required (although they are expected and hoped for). Fleet operators renting vehicles out to the public would qualify if the sales quantity is met.
An example of a "yes" resolution in the US would be a street-legal car which is also legal to fly under 14 CFR 23, 25, 27, 91, 103, or equivalent, and can be operated by anyone with a driver's license and appropriate flight certificate (or none, in the case of §103 and/or potential self-driving capability).
This question is focusing on sales because some street legal flying cars already exist in 2023, but there is no widespread adoption and it's not clear when/if mass-production and adoption of flying cars will arrive.
Hopefully the resolution criteria are clear enough; please provide recommendations if any further clarification is needed, and I'll review and add to the description.
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If you don't like the MPG of your ground car, you've not seen nothing yet.
Out of pocket cost, per passenger mile, unavoidable and due to energy, in low to high order:
train, or large passenger aircraft
motorcycle
car
Flying car that's like a small winged aircraft.
Helicopter, or boxy car shaped flying car.
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There is a town/village in the USA where they've pulled this off, where nearly everyone is a pilot, and they drive their "flying cars" out of their garages at home to the local runway, and then take off. They all look like small 1/2 occupant aircraft, just small enough to fit on the road, because they are.
@Elliot_dev if it's street-legal and also flies legally and makes up more than 1% of new sales, then it would count. Being operated by the person sitting in it is irrelevant to the resolution. See the last part of this paragraph from the description: "An example of a "yes" resolution in the US would be a street-legal car which is also legal to fly under 14 CFR 23, 25, 27, 91, 103, or equivalent, and can be operated by anyone with a driver's license and appropriate flight certificate (or none, in the case of §103 and/or potential self-driving capability)."
@Elliot_dev And as far as whether it makes sense to build a combo vehicle instead of just an air vehicle and a ground vehicle, that's essentially the question here. Does the convenience beat the inefficiency? Will FSD be relevant, if it happens?