Originally Posted by
Dr. HFH
Data point: I'm on a DONE3. This past Sunday, my first two flights were to be AA metal, AA marketed, NRT-DFW-BOS. Entire itinerary is credited to QRPC. Multi-hour delay of the inbound aircraft at NRT resulted in AA spontaneously rerouting me NRT-BOS on JL metal, AA flight number. When I was entering the Sakura Lounge, I asked the receptionist to check to see if my FFNO was in the record, since it didn't appear on my BP. It wasn't, so she added it. (AA apparently had created a separate, one-flight PNR for NRT-BOS without my FFNO.) After the flight, I checked, and it had credited correctly.
I did it a number of times exactly like Abidjan's colleague wants to. Back when AB had a status match from *A, I would put my AB number on the res, check in, use the lounge and change it to my BA or AA number before boarding. Never had an issue, though there's always a risk that it doesn't work and miles go the wrong place.