http://www.klm.com/travel/cz_en/prep...ance/index.htm
Baggage and transferring
If your trip includes a transfer, your check-in baggage is usually labelled to be sent to your final destination. This means that your baggage will automatically be put onto the next flight.
There are a few exceptions to this rule:
• If you have purchased two or more tickets from different airlines that have dissimilar conditions
• If you transfer from an AIR FRANCE or KLM flight to a domestic flight such as a domestic flight in the United States
• If you arrive at one airport and depart from another airport
• If your transfer lasts longer than 12 hours or your next flight departs the next day (when transferring at Amsterdam Airport Schiphol or Paris-Charles de Gaulle), you can ask for your baggage to be labelled to your final destination
• If you make a stopover
• If part of your itinerary includes bus or rail transport