We're often asked which of the planes using Shannon Airport are US military planes. The answer is that quite a lot of them are. In addition to the ones operated directly by the US Air Force, Navy and Army there are no fewer than 24 companies that have what are called "indefinite-delivery/indefinite-quantity" contracts to provide international airlift services to the US military.
If you see any of these planes at Shannon they could be carrying armed US soldiers or cargo. They are technically classified as "civilian" but in reality they are operating as US military planes.
If you see one of them, ask the authorities to verify what is on it, and where it is going or coming from. Chances are, it has weapons, weapon parts or ammunition on board.