We do a lot of traveling right now and nearly all of it involves waiting for customs and immigration, time zone changes, and middle-of-the-night flights. The kids are good sports with the schedule disruptions and having to leave most of their toys at home.
One toy that we do usually bring is colored pencils and paper. There are countless ways to use this to entertain kids of all ages, but mine are small and mostly use it for scribbling (Dalton) or drawing dinosaurs (Maggie).
On our most recent trip, I used the colored pencils to make a road on the airplane tray table for Dalton to drive his car on. Maggie calls this a “car play place.” I just drew a quick road and some familiar sites such as our apartment building, the post office, and Daddy's work. This entertained him for at least ten minutes, plus the five it took me to draw it. You can buy or make actual toys like this, but I like this paper version – simple, frugal, and it can be left behind.
Don't look too closely – Indians drive on the left, and I drew the lights and stop sign on the left side of the road without even thinking!
I've also done this on the back of restaurant place mats with a pen and a car from my purse. It's a fast way to distract hungry kids while waiting to be served.