you can learn a lot about a person by travelling with them
And you don't even need to travel to a different country with them. Travelling through an airport with someone is enough to learn a lot about them.
Have they checked in beforehand? Did they bring a snack from home? Or are they buying food there?
And what do they do while they wait for the flight? Do they scroll on their phone? Answer work emails? Read a book?
How is their mood while travelling? Are they stressed? Or completely chilled out?
Oh, and especially - how big is their bag? Are they a light or heavy packer?
In the questions above, there isn't a right or wrong answer. For example, a chilled out person may not always be a good thing if both are you are chilled - you may miss your flight!
The answer to the questions aren't important, but the act of asking the questions are. You'll start to notice small things about people that you normally wouldn't.
Also in my first draft of this, I almost missed my flight despite being an hour earlier than my colleagues (they had to block the airport door so I had a fighting chance). I wonder what that says about me lol.