 Tensions between the United States and Libya heightened after the hijacking of TWA Flight 847 on 14 June 1985, and the Rome and Vienna airport attacks on 27 December, that same year.The United States claimed that the Libyan leader was involved in these actions through his support of the alleged perpetrator, Palestinian terrorist Abu Nidal.At the same time Libya began the installation of SA-5 surface-to-air missile batteries and radars they received from the Soviet Union in late 1985, to bolster their air defense.