Cars: Both kids hate cars, but our daughter really really hates them. She gets carsick and dreads getting in the car. Thankfully, they also tend to knock her out so eventually she falls asleep.

Planes: The kids do great on planes, especially if we plan ahead and keep them entertained. We flew out to LA recently, and there was a lot of turbulence which triggered some airsickness. But it wasn't as bad as it coud've been, plus I think all the vibrations helped knock the kids out.