I have traveled extensively with both my kids (now ages "almost 4" and 2). For a 3-year-old, I don't bring a car seat. The regular seat belt works fine for my guy. Do not count on food or drink in the airplane, and expect to be delayed. From my experience, with all the cost-cutting and consolidation of flights going on at the airlines, almost nothing leaves on time. So bring plenty of snacks. Lollypops and lifesavers are great if her ears start to hurt. The airlines also allow sippy cups for kids. If you have or can borrow one, definitely bring a portable DVD player with one or two new movies that your daughter hasn't seen. I would also get a few new, small things she hasn't seen before and save them for the plane. Some ideas: coloring books with NON-ROLL crayons (Crayola makes them and they are essential if you don't want to chase crayons under the seats the whole flight), Color Wonder books and markers (neat), sticker books, little dolls or action figures-- all of these will help in the airport, on the plane, and during the inevitable delay. Oh, and if your daughter still has one, use your stroller right up to the gate of the plane-- you can gate-check it and you won't have to lug all your stuff through the airport. Good luck!