No, if controlled. As long as your crohn's disease is under control and followed by your doctor and/or gastroenterologist, you should be ok with flying. If you are having bleeding, symptoms of infection, or diarrhea, you may want to evaluate with your doctor if that particular time is safe for you to be on a long-distance flight. You also have to consider if you will have medical access if going overseas.
No. Just that you are traveling to places that you can get good medical care if you undergo an acute flare up.