The problem may be the water, people are very panicky about liquids (don't ask why) on planes.
The answer would probably be no, although they may allow it. If they do allow them, its probably in the cargo area of another plane. Unless they cargo hold has enviromental controls, it could get below freezing depending on the section, plane and how high they are cruising. To put things in perspective, normal cruising altitude is 30,000 ft or more in a jet, at that altitude it gets upwards of -30 degrees, celcius. To give you a rough estimate, back a couple of days ago, it was -41.2 degrees C at 30,000 feet where I live, I don't know about you, but that is cold. and more often then not, the amount of insulation in those cargo holds in little to nothing.
Your best bet is going to be mailing the plants to where ever you are going, yes they are not going to get there when you arrive possible, but they would more than likely arrive in good if not excellent condition.
