I believe an express subway line can do a better job. Though the initial cost for building new infrastructure is high, it also have the other two benefits you mention: Bypass all ground traffic and being very predictable (in fact more predictable than flying cars as it won't be impacted by whether). Moreover it can carry much more people at much lower cost. The benefit of high capacity could probably compensate for the high initial cost.
If regular subway is not fast enough, maglev train like the one connecting PVG airport to Longyang Rd subway station can complete its 19 miles trip in 8 minutes, with a fare less than 10 US dollars, and it has been running for almost two decades.
I’m just saying, we need to find other applications for this new technology. If we just want to connect city center to airports I’d so much prefer that people invest their money on trains which is a solution that can benefit lots of people rather than a just a few riches
For a technology to eventually become mainstream, usually it first needs to find a sweet-spot where operational kinks can be worked out. Think of Tesla Roadster.
It may add value if you could suggest a more suitable initial application than airport shuttle.
The original plan was to run it to the "city centre" at People's Square and then on to the other airport in town Hongqiao. The problem was expense, and for money to be a problem for the infrastructure-happy Chinese, you know its not economically viable for the majority of countries on earth.
The problem is not simply expense but whether the expense is worthwhile. Given Shanghai is already connected by a subway web, the benefit of directly connecting two airports with maglev is very questionable.
Maglev is just a bit extreme but more traditional subway systems are already super common across the world. The RER trains in Paris is exactly what I mean by an express subway system. It’s much faster than the other metro system in Paris simply because it has fewer stops.
If regular subway is not fast enough, maglev train like the one connecting PVG airport to Longyang Rd subway station can complete its 19 miles trip in 8 minutes, with a fare less than 10 US dollars, and it has been running for almost two decades.