Yes. It's completely rational for people to be scared out of their wits in an airplane, or higher than say twice the distance of a tree. No primate is in either situation, it's just not natural. What's different is the ability for many people to distract themselves, they have a more effective coping mechanism. There really isn't much distraction on an airplane for people who either do not read magazines/books, or watch tons of TV and movies. That's pretty much the only distraction an airplane has to offer.