Before the merger, my flights always posted immediately. At some point after the merger, this changed to 2 days after. I remember noticing the change. Is it possible that they feel that there needs to be some time for any issues to be resolved prior to posting? I'm sure they could post immediately if they wanted. If I buy something using MileagePlusX, the points post immediately. Funny that it takes longer for flights to post than for some other mileage earning methods.