During travels it’s most of the times inevitable to do longer rides with trains or busses. But also there it’s no problem to train the supporting strength, the triceps and the shoulders with a few “dips”.
During a stopover I stand on the corridor between to chairs, place my hands on the top of the back of the chairs, jump off and support myself with straight arms on them. The feet are in the air. Then I start to lower my body as far as I can and then I push it back up.