In the early days flights used to have several stops for refuelling, etc. KLM had an Amsterdam-Jakarta (then called Batavia) before WW II with several stops and it was possible to buy tickets for only part of the route.
KLM789 is a flight starting and ending in AMS with two stops in the Caribbean (SXM and CUR), allowing flights from Amsterdam to either of the islands (and a return). Another example is QF2 (LHR-DXB-SYD).