When I'm traveling, it seems the easiest snacks to come by are sweet ones. What with baked-on-board cookies, go-to trail mix, and sweet fruits galore, it's easy to start feeling a little dizzy with all of that sugar and so little substance. I've found that the snack I want to keep at hand when I'm traveling is easy, filling, and savory. It's an avocado!
While Emma goes so far as to spread hers on toast for early morning flights, I honestly just toss a ripe (but firm-ish) avocado into my carry-on (and a couple of unripened ones into my checked luggage).
While it's not ideal, opening an avocado on a plane isn't too tough or messy. It can be done by peeling from the stem or pushing a spoon into the skin. Eat as-is or ask the flight attendant for a lemon wedge (they have them on hand for drinks) and a salt packet if you want to dress it up.
By the time you're set to return home, those unripened ones in your checked luggage will be ready to go!