The drinking age on an airplane is generally determined by the country where the airline is registered, though this can change depending on the flight's route. For U.S.-based carriers like Delta, United, and American Airlines, the drinking age is 21, regardless of whether the flight is domestic or international. On most European and Asian carriers, such as British Airways, Lufthansa, or Emirates, the drinking age is 18, reflecting the laws of their home countries. However, there are nuances: some airlines may choose to follow the laws of the departure or arrival country while in that country's airspace, though most stick to their "flag carrier" rules for simplicity. Additionally, while the legal age on an Emirates flight might be 18, they will not serve alcohol on flights to certain strictly "dry" countries like Saudi Arabia. It is also important to note that cabin crew have the absolute right to refuse service to anyone they believe is intoxicated or underage, as safety and order in a pressurized cabin are the highest priorities for the flight crew in 2026.