To add your American Airlines (AA) AAdvantage number to an Alaska Airlines flight, you should ideally do so during the booking process by selecting "American Airlines" from the frequent flyer program dropdown menu and entering your number. If you have already booked, you can log into your reservation on the Alaska Airlines website or app using your confirmation code and look for the "Passenger Information" or "Add/Change Frequent Flyer Number" section. If you encounter issues online, you can ask a gate agent or check-in clerk at the airport to manually add it to your record. Since both airlines are members of the oneworld alliance, adding your AA number allows you to earn AAdvantage miles and Loyalty Points on Alaska flights, and if you have AA status, it ensures your benefits—such as priority boarding and checked bag allowances—are recognized during your journey.