I have had to buy tickets domestically in US for my parents, who would be connecting straight from a ex-MEL flight in LAX - obviously I would not be with them at the time. I asked about this issue as I knew the purchasing cc was needed. I was told I could go into LAX on a prior date and present the card to a check in agent and explain the situation, and this would be noted on my parents' record so they would have no problems.

I did as instructed and it worked out fine for them. I believe it was UA.