We recently got a sourdough starter, and have loved trying out many different recipes with it.  In a few weeks we will by flying home (after spending the summer in Alaska), and we would really like to take the starter home with us.  What's the best way to get it safely through the airport? 
If you don't want to transport liquid (= active) sourdough because you don't want to risk it to spill out of your container, note that you can either    mix some of it with more flour than usual until you get a dryish crumbly mass that can be stored in a plastic box or bag or spread a thin layer on parchment and dry it. Break up the "sheet" and store it in a dry place.   Both forms should be safe to be transported in either your checked baggage or in your carry-on luggage. Be prepared to answer questions from security either way. But I suppose liquid sourdough might raise the same questions.  At your destination, rehydrate the crumbs, add them to your usual water / flour mix and continue cultivating it as before. A few feedings should be enough to get the sourdough back into good shape. 