My first post in the hope one of you wise people can advise me . I was travelling with my brother on a BAH booking last month . LHR to SFO with BA and then codeshare SFO to LAS on Alaska , all under one booking . At check in at T5 the bags were ticketed through to LAS but they could only print boarding passes for LHR to SFO and said we would need to go to the Alaska desk in SFO for the SFO to LAS boarding passes . We got to security where we had a red light when scanning the boarding passes and were sent back to check in . Check in says " everything OK " and sends us back to security . Security says " no it isn't " and sends us back to check in . Over an hour later involving four different BA reps , two more failed trips to security , and two phone calls to I believe someone in IT and we finally got a green light . The reason given was that there was no passport number registered for the internal flight with Alaska .

When we got to SFO and went to the Alaska check in desk they printed out the boarding passes straight away with no problem .

We are flying the same itinerary next month and do not want the same mess . We have the booking reference for the Alaska flight and went into the booking to see if we could input passport details but could not see any option to do so . Any ideas/suggestions ? For reference we flew a similar itinerary in March , the only differences being we flew the first leg with AA from T3 to Seattle, and both boarding passes were printed at LHR with no security issues .