The following as specifically excluded in the fine print: Airline ticket purchases, mileage point purchases, mileage point transfer fees, gift cards, duty - free purchases, award tickets and fees incurred with airline alliance partners do not qualify. (doctorofcredit.com)
And there's a long list of exclusions, including airline tickets, upgrades, mileage points transfer fees, gift cards and any purchase not charged by the designated airline, such as a wireless internet pass at the airport. (creditcards.com)
From the terms and conditions: «Airline tickets, upgrades, mileage points purchases, mileage points transfer fees, gift cards, duty free purchases, and award tickets are not deemed to be incidental fees.» (singleflyer.com)