The 1% figure sounds insane, but remember that "11% of the world’s population took a flight in 2018". In other words, about 10% of the flyers cause half of aviation emissions.
https://thepointsguy.com/2017/09/american-airlines-amazing-s...
See Fig. 7 in the research paper linked in this article: https://www.sciencedirect.com/science/article/pii/S095937802...
It seems about 87%-53% = 34% of Americans fly once a year.
See Fig. 1: https://www.sciencedirect.com/science/article/pii/S095937802...
China and other countries did not report numbers so any analysis will be pure guesswork. The flat out comparison to miles flown by those on the continent of Africa exposes the nature of these types of studies. They have their observation written before the numbers are assembled.
To be honest the article is relying on the "one percent" theme which has been an all to common politically led class warfare action by which new policies and taxes are to be implemented under the guise of only targeting a limited set of people but in fact will impact many more and expanded at will once in place.
Class warfare is a common method to get a foot in the door. By incessantly portraying all problems as caused by "one percent" it becomes very easy to implement fees and taxes which will naturally have expand to include more than the "one percent" as the revenue will never meet the promised numbers.
That sounds implausible to me. Perhaps by dividing the number of flights by the world population. But I can't conceive more than 800,000,000 different people flying last year
[0] https://www.cnbc.com/2017/12/07/boeing-ceo-80-percent-of-peo...
Finally, we have to consider the percentage of flights taken by people who fly more than once a year, which probably represents a majority of seats.
All in all, it probably still lines up with 10%. It's shockingly high to me as well…
[0] https://www.statista.com/statistics/564717/airline-industry-...