After you step out of the airport, hold on to your boarding pass. If you're a member of a frequent-flyer program, but flew on a partner airline, there's always a chance a hiccup can occur — plus it's potentially good for taxes.
Photo by tacvbo.
Many airlines let you earn miles through alliances or partnerships. Even though it should be sufficient to give the airline your frequent flyer information, it may still be wise to keep your boarding pass around. John Hamilton, a member of Air France's Flying Blue program, ran into a problem in getting his Delta miles credited. They required him to have an original copy of the boarding pass even though Delta is a codeshare partner.
I was actually in a very similar situation last year. Continental switched to Sky Alliance, one of the biggest airline alliances in the world. I happened to be in the middle of a trip abroad on a Sky Alliance partner. Even though I gave Asiana Airlines my frequent flier information, I saved my boarding pass. When the miles didn't appear in my Continental account, I filed a retroactive claim. As a result, I was credited for 9500 miles — and now I always save my boarding pass.
Another solution, if you prefer to check-in online: Print two copies of your boarding pass so you can retain one for your records. The other one can be used to check-in and to trash (as most people are apt to do).