How to spend time usefully while traveling

I travel often, so I have already visited 66 countries. In the last three years, I had about 40–50 flights a year, visited many new countries and spent quite a lot of time on the road. For example, last year I spent one week in the sky, and another two weeks only on the way to an airport and a city. When there are so many trips, then this is no longer a vacation when you disconnect from everything and relax, but try to organize this time, and use it for self-development, otherwise, you will lose a lot of time.