But despite this, I mostly agree with the broader premise.
Total passenger miles have been largely flat since 2000. Total departures actually fell during the aughts, along with jet fuel consumption. Some of that's due to more efficient flight booking (appropriately sized aircraft, higher seat utilisation), though a large share is decreased seat pitch, which is to say, far less comfortable travel.
https://www.economist.com/img/b/1280/670/90/sites/default/fi... https://cdn.statcdn.com/Infographic/images/normal/16947.jpeg
Global incomes have risen, most notably in China.
I may have misread a chart or mis-remembered statistics. The Statista chart does show that the post-2000 trend in air travel is well below the 1990s trendline. Actual miles travelled would have been above 1 trillion had the former continued.
The more notable chart of Gordon's does indeed show price per passenger mile, not total miles (p. 401, Rise and Fall).
It's also often useful to think of travel not as miles but as time. Given an average train speed of about 30 mph, and aircraft of about 450 mph, the time per person per travel mode is nearly identical: 1.3 vs. 1.6 billion hours.
People take trains. They don't take them as far as they do aircraft.
Auto travel works out to about 12 billion hours, again assuming 30 mph average speed. That's about 10 minutes per person per day.
I've yet to find a good presentation of long-term trends.