When doing a plan and book itinerary the system brings up invalid options - i.e. after booking a CPT - LHR - JFK - HKG is you then put in to do and HKG - JNB I regularly get the option of HKG - JNB on cx which is fine, but the next option is usually HKG - LHR - JNB or even HKG - HEL - LHR - JNB - neither of which are valid. I've also been offered for a JFK - GIG the routing JFK - LHR - GIG