Seaborne Airlines today announced the introduction of a new interline agreement with United Airlines providing customers convenient connections between the networks of United and Seaborne Airlines.   Now customers have the convenience of purchasing a single ticket for United and Seaborne Airlines services, checking baggage at their origination to their final destination, and easy connections at Luis Munoz Marin Airport in San Juan, PR (SJU) to exciting destinations, including St. Thomas, St. Croix, Dominica, Fort de France, Martinique, Point a Pitre, Guadeloupe, La Romana, DR, Punta Cana, DR, Santo Domingo, DR, St. Maarten, St. Kitts and Nevis.