[mrpopo]

1) This is a false dichotomy. We need to reach net zero by 2050 to keep warming below 2 degrees (if we're lucky), therefore we need to solve both.

2) The 100 million people who fly have the most concentrated wealth and therefore have more leeway to implement alternatives to flying (high-speed rail for flights within the US for example).

3) You could also imagine the 100 million people investing to build new low-carbon electricity generation infrastructures in developing countries via a carbon tax on their flight ticket. Of course, they could donate directly as well, either solution is fine. That was actually the spirit of the Paris agreement, which Trump walked out of. Since the 100 million people who fly actively refuse to let go of their wealth, alternative options such as 2) are being considered, even though they might have lower impact (since they affect on the 2.5% of GHG emissions instead of the 25% of GHG emissions).

[melling]

If we had addressed the coal problem 2 decades ago, our net zero goal would have been 2060 or 2070?

Ignoring the coal problem, and actually greatly increasing the coal usage in the past 20 years, has pushed us into a corner where we need miracles. Now "everything" must be addressed!