Article 18 imposing liability for destruction or loss of baggage by an "occurrence," implies that the drafters of the Convention understood the word "accident" to mean something different than the word "occurrence." Moreover, Article 17 refers to an accident which caused the passenger's injury, and not to an accident which is the passenger's injury. The text thus implies that, however "accident" is defined, it is the cause of the injury that must satisfy the definition rather than the occurrence of the injury alone. And, since the Warsaw Convention was drafted in French by continental jurists, further guidance is furnished by the French legal meaning of "accident”—when used to describe a cause of injury, rather than the event of injury-as being a fortuitous, unexpected, unusual, or unintended event. Pp. 397–400.

(b) The above interpretation of Article 17 is consistent with the negotiating history of the Warsaw Convention, the conduct of the parties thereto, and the weight of precedent in foreign and American courts. Pp. 400-405.

(c) While any standard requiring courts to distinguish causes that are "accidents" from causes that are "occurrences" requires drawing a line that may be subject to differences as to where it should fall, an injured passenger is only required to prove that some link in the chain of causes was an unusual or unexpected event external to the passenger. Enforcement of Article 17's "accident" requirement cannot be circumvented by reference to the Montreal Agreement. That Agreement while requiring airlines to waive "due care" defenses under Article 20(1) of the Warsaw Convention, did not waive Article 17's "accident" requirement. Nor can enforcement of Article 17 be escaped by reference to the equation of "accident" with "occurrence" in Annex 13, which, with its corresponding Convention, expressly applies to aircraft accident investigations and not to principles of liability to passengers under the Warsaw Convention. Pp. 405-408.

724 F. 2d 1383, reversed and remanded.

O'CONNOR, J., delivered the opinion of the Court, in which all other Members joined, except POWELL, J., who took no part in the consideration or decision of the case.

Stephen C. Johnson argued the cause for petitioner. With him on the briefs was Lawrence N. Minch.

Carroll E. Dubuc argued the cause for the Republic of France as amicus curiae urging reversal. With him on the brief was Peter Hoenig.

Bennett M. Cohen argued the cause for respondent. With him on the brief were Daniel U. Smith and Albert R. Abramson.* *

JUSTICE O'CONNOR delivered the opinion of the Court.

Article 17 of the Warsaw Convention' makes air carriers liable for injuries sustained by a passenger "if the accident which caused the damage so sustained took place on board the aircraft or in the course of any of the operations of embarking or disembarking." We granted certiorari, 469 U. S. 815 (1984), to resolve a conflict among the Courts of Appeals as to the proper definition of the word "accident" as used in this international air carriage treaty.

I

On November 16, 1980, respondent Valerie Saks boarded an Air France jetliner in Paris for a 12-hour flight to Los Angeles. The flight went smoothly in all respects until, as the aircraft descended to Los Angeles, Saks felt severe pressure and pain in her left ear. The pain continued after the plane landed, but Saks disembarked without informing any Air France crew member or employee of her ailment. Five days later, Saks consulted a doctor who concluded that she had become permanently deaf in her left ear.

Saks filed suit against Air France in California state court, alleging that her hearing loss was caused by negligent maintenance and operation of the jetliner's pressurization system. App. 2. The case was removed to the United States District Court for the Central District of California. After extensive

*Briefs of amici curiae urging reversal were filed for the United States by Solicitor General Lee, Acting Assistant Attorney General Willard, Deputy Solicitor General Geller, Alan I. Horowitz, and Mark H. Gallant; and for the International Air Transport Association by Randal R. Craft, Jr.

1 Convention for the Unification of Certain Rules Relating to International Transportation by Air, Oct. 12, 1929, 49 Stat. 3000, T. S. No. 876 (1934), note following 49 U. S. C. App. § 1502.

discovery, Air France moved for summary judgment on the ground that respondent could not prove that her injury was caused by an "accident" within the meaning of the Warsaw Convention. The term "accident," according to Air France, means an "abnormal, unusual or unexpected occurrence aboard the aircraft." Id., at 9. All the available evidence, including the postflight reports, pilot's affidavit, and passenger testimony, indicated that the aircraft's pressurization system had operated in the usual manner. Accordingly, the airline contended that the suit should be dismissed because the only alleged cause of respondent's injury-normal operation of a pressurization system-could not qualify as an “accident." In her opposition to the summary judgment motion, Saks acknowledged that "[t]he sole question of law presented

by the parties is whether a loss of hearing proximately caused by normal operation of the aircraft's pressurization system is an 'accident' within the meaning of Article 17 of the Warsaw Convention . . . ." Id., at 30. She argued that "accident" should be defined as a "hazard of air travel," and that her injury had indeed been caused by such a hazard.

Relying on precedent which defines the term "accident" in Article 17 as an "unusual or unexpected" happening, see DeMarines v. KLM Royal Dutch Airlines, 580 F. 2d 1193, 1196 (CA3 1978), the District Court granted summary judgment to Air France. See also Warshaw v. Trans World Airlines, Inc., 442 F. Supp. 400, 412-413 (ED Pa. 1977) (normal cabin pressure changes are not "accidents" within the meaning of Article 17). A divided panel of the Court of Appeals for the Ninth Circuit reversed. 724 F. 2d 1383 (1984). The appellate court reviewed the history of the Warsaw Convention and its modification by the 1966 Montreal Agreement, a private agreement among airlines that has been approved by the United States Government. Agreement Relating to Liability Limitations of the Warsaw Convention and the Hague Protocol, Agreement CAB 18900, 31 Fed. Reg. 7302 (1966), note following 49 U. S. C. App. § 1502. The court

concluded that the language, history, and policy of the Warsaw Convention and the Montreal Agreement impose absolute liability on airlines for injuries proximately caused by the risks inherent in air travel. The court found a definition of "accident" consistent with this history and policy in Annex 13 to the Convention on International Civil Aviation, Dec. 7, 1944, 61 Stat. 1180, T. I. A. S. No. 1591, 15 U. N. T. S. 295; conformed to in 49 CFR § 830.2 (1984): "an occurrence associated with the operation of an aircraft which takes place between the time any person boards the aircraft with the intention of flight and all such persons have disembarked . . . . 724 F. 2d, at 1385. Normal cabin pressure changes qualify as an "accident" under this definition. A dissent agreed with the District Court that "accident" should be defined as an unusual or unexpected occurrence. Id., at 1388 (Wallace, J.). We disagree with the definition of "accident" adopted by the Court of Appeals, and we reverse.

II

Air France is liable to a passenger under the terms of the Warsaw Convention only if the passenger proves that an "accident" was the cause of her injury. MacDonald v. Air Canada, 439 F. 2d 1402 (CA1 1971); Mathias v. Pan Am World Airways, Inc., 53 F. R. D. 447 (WD Pa. 1971). See 1 C. Shawcross & K. Beaumont, Air Law ¶ VII(147) (4th ed. 1984); D. Goedhuis, National Airlegislations and the Warsaw Convention 199 (1937). The narrow issue presented is whether respondent can meet this burden by showing that her injury was caused by the normal operation of the aircraft's pressurization system. The proper answer turns on interpretation of a clause in an international treaty to which the United States is a party. "[T]reaties are construed more liberally than private agreements, and to ascertain their meaning we may look beyond the written words to the history of the treaty, the negotiations, and the practical construction adopted by the parties." Choctaw Nation of Indians v. United States, 318 U. S. 423, 431-432 (1943). The

analysis must begin, however, with the text of the treaty and the context in which the written words are used. See Maximov v. United States, 373 U. S. 49, 53–54 (1963).

A

Article 17 of the Warsaw Convention establishes the liability of international air carriers for harm to passengers. Article 18 contains parallel provisions regarding liability for damage to baggage. The governing text of the Convention is in the French language, and we accordingly set forth the French text of the relevant part of Articles 17 and 18 in the margin. The official American translation of this portion of the text, which was before the Senate when it ratified the Convention in 1934, reads as follows:

2

"Article 17

"The carrier shall be liable for damage sustained in the event of the death or wounding of a passenger or any other bodily injury suffered by a passenger, if the accident which caused the damage so sustained took place on board the aircraft or in the course of any of the operations of embarking or disembarking.

"Article 18

"(1) The carrier shall be liable for damage sustained in the event of the destruction or loss of, or of damage to, any checked baggage or any goods, if the occurrence

"Article 17

"Le transporteur est responsable du dommage survenu en cas de mort, de blessure ou de toute autre lésion corporelle subie par un voyageur lorsque l'accident qui a causé le dommage s'est produit à bord de l'aéronef ou au cours de toutes opérations d'embarquement et de débarquement.

"Article 18

"(1) Le transporteur est responsable du dommage survenu en cas destruction, perte ou avarie de bagages enregistrés ou de marchandises lorsque l'événement qui a causé le dommage s'est produit pendant le transport aérien." 49 Stat. 3005 (emphasis added).

Article 36 of the Convention recites that it is drawn in French. Id., at 3008.