Certain airline gift card purchases in smaller denominations are known to work. (pointsyak.com)
However, you can use them toward airline gift cards purchased directly from the carrier, which you could then use to book a flight. (thepointsguy.com)
But, you might ask, if you can't get credit for airline gift cards purchased during the last month, doesn't this mean you're stuck with unreimbursed airline gift cards? (travelcodex.com)