My father retired as a Captain for United Fruit Company. The last American flag ships were
twin screw -- delivered in 1945-1946 -- Fra Berlanga, Junior, Limon, San Jose, Esparta and Comayagua;
Single screw -- delivered in 1947-1948 -- Yaque, Cibao, Quisquea, Santo Cerro, Sixaola, Tivives, Hibueras, Ulua and Morazan.
All these ships were contracted to MSTS during the Vietnam War and provided refrigerated shipping (and even warehousing) for the War Effort. Meanwhile, the Company chartered foreign flag ships to continue the delivery of fruit from South and Central America to the US. With the end of major US involvement the war in 1972, the ships were returned to the Company. It was deemed 'too expensive' to use U.S. Merchant shipping and the ships were sold and the mariners forced to retire or seek employment elsewhere.