Definitely take it with you on the plane. We've been seeing some horror stories about lost baggage on the news lately, and there's no way I'd let a dress out of my sight if traveling by plane. It's not like you can go out and get a new one.
This is a pretty good article on packing a wedding gown for travel, so it should help you.
http://www.destinationbride.com/features/wedding-articles/destination-wedding-gown
Basically, If you would rather pack the gown yourself, line the box with tissue and lay the gown face down in the box so that the top of the gown extends beyond the box, the middle of the gown is in the box, and the train also extends beyond the box. Make sure you have the gown centered in the box and that the part that is face down is spread flat so there are no creases or folds.
Beginning at the side seams, fold the skirt lengthwise over bunched tissue until the skirt is no wider than the box. Then add more tissue and fold the bottom of skirt over into the box. Add still more tissue and fold the top of gown over so that it, too, fits into the box. Think of the gown as your body and that you are doing the impossible: laying on your stomach with your legs folded up over your back at the same time your head and shoulders are bent back over your legs and facing up. Now use still more tissue to stuff the bodice and sleeves, if there are any. When you are finished, the dress should not be able to move around in the box
Can you get it pressed when you arrive?