I went to fly a multiple leg flight in europe. Flew EGBB to EDDK then wanted to go on to LOWI. Using FSNav4.5 planned first leg, loaded into FMC and flew with no problems. On arrival at EDDK planned next leg but when I went to load the plan into the FMC it wasn't available for import. (I cleared out the first legs route) Had to select a different acft, then reselect the DF737 and the plan was now available for loading. Does anyone know a way round this or do I have to plan and save all legs before starting up with the DF737.