A version of that for cars is common enough actually. Several countries and US states have road worthiness tests that include minimum (maximum?) emissions standards that must be met. The car I drive will probably ultimately fail on emissions as standards rise over the next few years.

Well, the curious fact is that small planes (Piston General Aviation, what is discussed here) emissions are comparable to cars.

Cessna 172 (trainer plane, not known for efficiency) burns 32 l (8.5 lb) per hour at a cruising speed of 122 knots (140 mph, 226 kph). Assuming no wind, it gives mileage of 14 l / 100 km (16.5 miles per gallon).

Taking into account that there are much less planes than cars, they emit 0.13% of all the CO2, emitted by transportation, comparing to 81% of motor vehicles (623 times less) [1]. So I would say their lead emissions are too low to bother (and mostly harm their owners who are close to the exhausts). Would be nicer, of course, to use unleaded, but not a big deal to lobby for legislations.

[1] https://communicatescience.com/zoonomian/tag/cessna-172/

I live in a county with emissions standards. Vehicles over 25 years old are exempt. There are reasonable ways to implement rising standards by exempting older ones.

I've lived in two places that required emissions testing. In both, the vehicles were held to the standard in place at the time it was built, not the current highest standard.

The larger private planes use kerosene, but smaller planes use gasoline just like they always did.

The difference is that new gasoline planes can work with unleaded.

They could be outlawed non-suddenly.

So many things were making it slowly less and less viable through extra costs/requirements would've likely been the better plan, but instead nothing changes until at some point there is enough pressure for change, and then there's complaints its "so suddenly". (I think with Avgas that has happened a tiny bit through storage regulations - its sufficiently more annoying to keep around that some places don't offer it anymore, making it a tiny bit less attractive for plane buyers)

Then people will just complain it's sudden when it gets close to the deadline.

Even cheap used small private planes cost > $100k. Since they are exclusively owned by wealthy people, it is a political impossibility to outlaw them.

> exclusively owned by wealthy people

You are underinformed. Most Cessna owners I know, are middle-income fanatics, usually co-owning a single plane.

I looked into the cost of flight lessons in a small plane, the cost of using an airport runway, and fuel. It was extremely expensive to me and I make 6 figures.

Then you have very different priorities than an airplane owner. You pay for plenty of things that are extremely expensive, you just choose different things.

I too make six figures, and I don't think I do anything as expensive as completing flight school and co-owning a Cessna. I mean, my house is more expensive than that, I guess, and my car is (barely) more expensive than flight school might be, but surely amateur pilots have houses and cars too. About the only expense I have that might come close to serious flying as a hobby would be pets, but outside of the one time we had to pay for chemo for our dog it's not that expensive.

What was your cost?

In US you can get a license for as low as $8k total. In expensive California, expensive SF Bay Area cost is around $15k total.

You're saying that amateur making six figures cannot find $15k for something they basically live for? Sounds very unlikely.

Btw, there's no cost of using airport runway, it's paid from your taxes.

There is no cost of using an airport runway, at least in the US...

We could buy them up and scrap them as their value declines while also working to outlaw 100LL at the ~4000 FBOs in the US that still carry the fuel. At some point, demand decline encounters an inflection point where it's no longer economically feasible ("death spiral") to continue to provide 100LL fuel to FBOs.

Cash for clunkers sort of thing.

Cash for clunkers was only tenable because the recipients of the cash were predominantly the working poor. Even then, economic conservatives howled at the program for its destruction of capital.

The first recipients were new car buyers. Hardly the working poor.

You could argue those buying new cars bought clunkers from the working poor for their above-market trade-in value, but that only works for the poor if they didn’t need to replace that clunker because everything used went up in price.

Most of the planes flying were made in 60's and 70's. Most of them can be bought below $100K. Most owners of 100LL burning planes are middle class. Wealthy people fly jets or at least turboprops and burn Jet-A.

I think deciding if something is unjust should factor in the impact. If someone has a 1990 Honda Civic that is their only means of getting to work and suddenly it's illegal due to pollution that's one thing. However if someone's private jet needs an expensive upgrade then that's another impact.

Wrong airplane. Jets use JET-A (no lead) not AVGAS

Don’t they need new engines at some point anyway?

Yeah, but you would need a new type certificate if the model of the engine is different from the version that was certified. Not to mention, you'd need a lead-free-compatible engine that physically fits into the plane.

True! But for many popular airframe/engine combinations there are companies which hold supplemental type certificates (STCs) for the conversion, see for instance Petersen Aviation who have a dedicated website for STCs covering conversion to auto fuel: https://www.autofuelstc.com/

I know some enthusiasts have been retrofitting with Subaru boxer engines with some success, but they end up with an X registration.