State immunity — Jurisdictional immunity — State corporation — Commercial activity exception — Requirement that activity having a direct effect in the United States — Aircraft purchased by United States corporation from foreign State-owned corporation — Aircraft crashing abroad killing its pilot — Whether suffering caused to family of deceased pilot in the United States a direct effect of crash — Whether financial loss incurred by owners of aircraft in the United States a direct effect of the crash — United States Foreign Sovereign Immunities Act 1976 — The law of the United States