After World War II a paved runway replaced the grass landing field and the Sixth Army Flight Detachment used Crissy Field for light utility and passenger planes, and helicopter operations. During the Vietnam war the Army used Crissy Field for liaison flights and MedEvac flights to transport wounded Vietnam soldiers from Travis Air Force Base to the Presidio's Letterman Army Hospital, a trip by ambulance on surface roads would take too long and possibly be delayed by traffic into San Francisco. At the end of the Vietnam war in 1974 the Army closed Crissy Field to airplanes, though helicopter operations continued for several years.