Deep Vein Thrombosis and Air Travel Group Litigation (8 actions) (formerly 24 actions)

For article 17 of the Warsaw Convention 1929, the accident is the cause of bodily injury, not the injury itself. It ordinarily requires an unexpected or unusual event or happening external to the passenger, assessed in the circumstances of the carriage.

A normal flight operated in accordance with ordinary airline practice, with no unusual external event, does not become an article 17 accident merely because a passenger suffers deep vein thrombosis. A failure to warn of the risk does not alter that conclusion where no warning was usual or expected. Fault and the carrier's ability to prevent injury cannot bypass the prior requirement of an accident.

The claimants brought group proceedings against commercial airlines after suffering, or alleging that deceased relatives had suffered, deep vein thrombosis during international flights. A specimen matrix assumed that the flight caused symptomatic DVT and that the airlines knew or ought to have known of an increased risk, but also assumed a normally operated aircraft, standard seating and cabin systems, and no warning or advice about DVT.

A preliminary issue asked whether the onset of DVT, whether caused by an act or omission of the carrier or otherwise, was capable in principle of being an accident causing bodily injury under article 17 of the Warsaw Convention 1929, incorporated by the Carriage by Air Act 1961. The Court of Appeal had answered no in In re Deep Vein Thrombosis and Air Travel Group Litigation [2003] EWCA Civ 1005; [2004] QB 234.

1. Appeal dismissed unanimously. Lord Scott, Lord Steyn, Lord Walker, Baroness Hale and Lord Mance agreed that the specimen matrix disclosed no article 17 accident.

2. Per Lord Scott, article 17 distinguishes the bodily injury from the accident causing it. The Convention's language, rather than a judicial paraphrase, remains the governing standard. The House nevertheless accepted the useful formulation in Air France v Saks 470 US 392 (1985): the causal event must be unexpected or unusual and external to the passenger.

3. Per Lord Steyn, the assumed ordinary and uneventful flight contained no such external event. The impact of the flight as a whole upon a particular passenger, resulting in DVT, was not itself an accident. Policy arguments based on the airline's control of the risk, capacity to insure, or alleged fault could not enlarge the treaty's language.

4. Per Lord Mance, the permanent features and normal operation of the aircraft were not an accident. The absence of a DVT warning was neither an event nor unusual or unexpected where it accorded with current industry and airline practice. Article 20 concerns the carrier's care in avoiding damage only after an article 17 accident has been established; it cannot be used to circumvent that requirement.

5. Lord Walker explained that a categorical refusal by cabin staff in an exceptional incident, as in Olympic Airways v Husain 540 US 644 (2004), was materially different from mere inaction during an ordinary flight. Baroness Hale similarly stressed that an internal reaction to an ordinarily uncomfortable journey, without anything untoward apart from that reaction, fell outside article 17.

• House of Lords: dismissed the claimants' appeal and upheld the conclusion that the agreed matrix disclosed no article 17 accident: [2005] UKHL 72.

• Court of Appeal: held that a standard flight and the alleged failure to warn of DVT did not constitute an accident under article 17: In re Deep Vein Thrombosis and Air Travel Group Litigation [2003] EWCA Civ 1005; [2004] QB 234.