State immunity — Attachment and execution — Whether immunity from execution more extensive than immunity from jurisdiction — State corporation — Airline — Whether assets of State corporation liable to execution to enforce judgment against foreign State — When separate identity of corporation should be disregarded — Joint participation in tort — Whether involving abuse of corporate form entitling court to disregard separate identity — Whether property in use for commercial purposes — Involvement of State corporation in political assassination of exile — United States Foreign Sovereign Immunities Act 1976 — Exception to immunity from jurisdiction in case of certain non-commercial torts — Different scope of exceptions to immunity from execution — The law of the United States