State immunity — Jurisdictional immunity — Subject-matter jurisdiction — Claim for damages for alleged conversion of aircraft by airport authority — Detention of aircraft pending payment by owners of aircraft of outstanding landing and parking fees incurred by lessee of aircraft — Commercial activity exception to immunity — Payment of fees causing plaintiff to suffer financial loss in United States — Whether sufficient to establish direct effect in United States — Whether foreign State’s commercial activities in United States can be attributed to airport authority to found jurisdiction — Expropriation exception to immunity — The law of the United States