I am in Amsterdam this week on business and I brought my flutes along for the trip since I have a performance this coming weekend when I return home. I didn't want to bother with carrying my flutes on the plane so I packed them into my checked baggage. First of all, I didn't pack any of my cherished flutes, as I didn't want to trust them to the checked baggage because I had to change planes in Houston. Secondy, I packed my flutes in the standard Laughing Mallard flute cases and the flute cases fit perfectly into my large TravelPro wheeled suitcase with enough room left for a weeks worth of clothes. Everything arrived in perfect shape. I've heard a lot of stories about folks getting stopped at security with their flutes, and I didn't want to bother with that issue either.
There are several online resources for information about traveling with musical instruments, and if you plan to travel with your flutes you should definitely check with the air carrier before arriving at the airport. If I was to bring along one of my invaluable flutes, like my Woodsong flute, I definitely wouldn't let it out of my sight. I always travel with at least one flute, usually one small enough to fit into my bag. The Ken Light PF Series is a great travel flute, BUT note that this flute isn't fingered in the 'easy tuning', rather Ken uses his own fingering. I don't recommend this flute as an entry level flute (it makes a great addition after you've learned to play the easy fingering... my opinion). Sam Kurz, also makes a 5N1 flute which breaks down into a nice compact package that is easily packable.
Here are some online resources for traveling with instruments:
Nation Association for Musical Education
American Federation of Musicians