+1 You can't make them do anything except sit in the car seat thanks to that 5-point harness.

If you resort to Benadryl, make sure you know how your child reacts to it. We gave it to our son for actual allergies and it wound him up like a triple espresso! His doc then prescribed juvenile Singulair which works great for him. That's when we learned that Benadryl doesn't make all kids sleepy.

Our best tips are planning, timing fllights to take advantage of nap and feeding times, comfy clothes, comfort toy and most important, make sure the parents are relaxed! Nervous/stressed out parents will give off a vibe that baby picks up on and that won't make for a good situation.