Tip: Always Add Your Frequent Flyer Number — Even on Award Tickets

Using your hard-earned points or miles for free flights (especially in premium classes) is a great way to make the most of your redemptions. However, occasionally an airline coding mistake could make this proposition even more lucrative, resulting in an award flight actually earning you miles. Even if you've redeemed miles for your ticket, always be sure to add your desired frequent flyer number on the off-chance that the flight credits as a paid fare class.

The first time I encountered this was back in 2013 when a friend received more than 12,000 SkyMiles after an Air France award ticket (booked through Delta) credited as a full-fare business class ticket. The comments section on that post turned into a spirited debate on whether my friend should notify Delta (he didn't), whether the miles would remain (they did) and whether airlines' fleecing of customers justified keeping them (jury's still out). I hadn't thought much of this until a very similar experience happened to me last year.

After redeeming miles through one Star Alliance program for a flight on a different carrier, I noticed that my family's last name was spelled wrong. A quick call was all it took to reissue the ticket, but this somehow changed our booking class from I (business class award) to Z (paid business class ticket). Intrigued, I added our United MileagePlus numbers to the reservation during check-in, and lo and behold, the flights posted just as a paid ticket would:

We can debate the moral implications of this type of mistake six ways to Sunday, but the bottom line is that it never hurts to add your frequent flyer number to an award reservation. Worst case scenario is that nothing happens. Best case scenario? You'll take home an unexpected windfall of miles to help you reach your next free trip.