Eastern wanted a third engine for its overwater flights to the Caribbean , since at that time twp-engined commercial flights were limited by regulations to routes with 60-minute maximum flying time to an airport ( see ETOPS\/LROPS ) . Eastern wanted a third engine for its overwater flights to the Caribbean , since at that time twin-engined commercial flights were limited by regulations to routes with 60-minute maximum flying time to an airport ( see ETOPS\/LROPS ) .