I have had some big errors fall my way, latest 2 were AA giving me 2 rt to NRT 1st class for 50,000 less ff miles than required for a trip I have next month. The second AA agent I talked to realized it was an error, but left it alone. DL gave me two 1st class rt to HNL last year for 60K ff miles instead of 120K. I even called to ask if I was only getting one ticket instead of two. Although I am the kind of guy that has returned lost wallets and I point out errors on receipts not in my favor, I didn't think these kind of errors had to be remedied. I think of these as "goodwill" errors that keep a good customer happy.