Air Force has halted some of the company’s initial work on a project to upgrade South Korea’s F-16 fighter jets amid ongoing talks about the second phase of the project. Air Force on the KF-16 upgrade program that has now resulted in a partial stop work order,” said BAE spokesman Brian Roehrkasse. South Korea last week said it could cancel the overall project to upgrade 134 F-16 fighter jets and seek a different contractor, after the U.S.