Which both cost billions over billions, and you will not achieve that good connection for the majority of citizens with just one line.

They're expensive, but massively more efficient than other transport. Plus they reduce congestion for anyone who doesn't have easy access.

I could understand why say, Lagos wouldn't have effective mass transit. But it's hard to see why major developed-world cities can't justify the investment.

I think people misunderstand my GP comment. I am VERY pro subway and public transport in general, and I go by bike whenever I can. But there’s a tool for every job, and one subway line won’t solve the same problem a thousand air taxis are going to solve. They don’t even play in the same league. One connects city parts loosely together and relies on other last-mile means of transport (walking, taxi, park&ride, kiss&ride, bike,...); while the other is a whole-in-one, it’s more exclusive (use once per month vs twice per day) and way faster (minutes instead of hours).

Do we need more subways? Heck yes! I want one in my hometown. Do we want air taxis at the same time? Well, why not?