I always save my boarding passes in case of problems. Today, with so many of us printing our own boarding passes long before we ever get to the airport, keeping a copy of your boarding pass is generally easy.

At the beginning of a trip when I print the boarding pass for my starting leg, I print an extra copy of the boarding pass and leave it at home.

When I’m at a hotel, while away from home, and print boarding passes during my trip, I do the same. I print an extra copy of the boarding pass and file it away with any other papers I keep for the duration of the trip (bills, receipts, fliers, brochures, etc.).

Sometimes it isn’t possible to print your boarding pass prior to getting to the airport. In that case I save my stub immediately after boarding in a zippered compartment of my personal bag I’ve brought on board with me so I don’t loose it.

Several years ago I had a similar problem. I flew with BMI between London and Edinburgh. US Air didn’t credit me for the flights, as of a month after I took them, which were not only important for the miles, but for my elite FF status level at US Air. I didn’t have my boarding passes (I didn’t know better then.) and asked US Air what I could do. They told me that if BMI would confirm I actually flew on their airline, they would properly credit me. I telephoned BMI and they told me mix-ups like this happen all the time. The sent me a letter confirming I flew on two of their flights, giving the dates, flight numbers, and class of seat. I forwarded the letter to US Air and within a week the flights were credited to my account.