Yes, active-duty U.S. military personnel can access American Airlines Flagship Lounges, but the rules are much stricter than those for the standard Admirals Club. To enter a Flagship Lounge, military members must be traveling in uniform on a pre-confirmed international flight operated by American Airlines. The flight must be a qualifying transoceanic route (like to Europe, Asia, or South America) or a qualifying long-haul transcontinental flight. Additionally, the member must present their active military ID and a boarding pass for a same-day flight. Unlike the Admirals Club, which offers broader access to military members on domestic leave with certain credit cards or memberships, the Flagship Lounge is an exclusive "Tier 1" space with premium dining and showers, so the "international/in-uniform" requirement is usually non-negotiable. If you are traveling domestically on leave, you are generally directed to the standard Admirals Club. However, if you are an elite status member (Platinum Pro or Executive Platinum) through a separate qualification, you can access the Flagship Lounge regardless of your military status on any qualifying international itinerary.