 The merged project continued under the JAST name until the engineering, manufacturing and development (EMD) phase, during which the project became the Joint Strike Fighter.The CALF was a DARPA program to develop a STOVL strike fighter (SSF) for the United States Marine Corps and replacement for the F-16 Fighting Falcon.The United States Air Force passed over the F-16 Agile Falcon in the late 1980s, essentially an enlarged F-16, and continued to mull other designs.