Abstract: For the unity of the rules of Jurisdiction in international air transport, article 33 of Montreal Convention 1999 inherited the article 28 of Warsaw Convention 1929, which prohibits the application of the doctrine of form non conveniens. For the purpose of protecting Americans, the fifth jurisdiction was incorporated in the MC99. In a recent case, U.S. court tried to separate the intrinsic link between the two conventions, holding that the doctrine of forum non conveniens could be applied in all of jurisdiction rules. From the perspective of treaty interpretation, there are four reasons which demonstrate such ruling was wrong. Firstly, the French version of MC99 on the different jurisdiction rules taking different words. Secondly, the purpose of unified jurisdiction and passenger protection and consumer protection show that the doctrine should not apply in four jurisdictions. Thirdly, Travaux Paratories indicated that codifying the doctrine was still suspending. All of the evidences show that the application room of the doctrine is limited to the fifth jurisdiction and can not extend to the other four jurisdictional rules. Thus, the practice of American courts is inconsistent with the MC99,which seriously derogated the unity of the treaty and the pursuit of protecting travelers.