Deep Vein Thrombosis and Air Travel Group Litigation

The House considered whether the onset of deep vein thrombosis (DVT) during international carriage by air can be an "accident" within article 17 of the Warsaw Convention 1929 (as amended). The court confirmed that for article 17 purposes the relevant "accident" must be a cause of the bodily injury and not the injury itself, and, adopting the test in Air France v Saks, must be an unexpected or unusual event or happening that is external to the passenger. The House held that ordinary conditions of air travel (for example cramped seating), and mere omissions by an airline to warn where there was no established practice of warning, do not amount in principle to an article 17 "accident". The appeal was dismissed on the assumed facts in the specimen matrix: a normal flight, no unusual event on board, and no established practice of warnings by the carrier.

This litigation arose as group proceedings in which claimants alleged that the onset of deep vein thrombosis (DVT) during or arising out of international flights was caused by an "accident" within article 17 of the Warsaw Convention and that carriers were therefore strictly liable for resulting bodily injury. A preliminary issue was directed and determined on an agreed specimen matrix of assumed facts: the flights were operated and equipped in the airline's usual manner, nothing unusual happened during the flights, it was assumed that the flight caused symptomatic DVT and for the purpose of the matrix it was assumed the airline knew or ought to have known of the increased risk but did not warn the passenger.

The nature of the claim: damages under article 17 of the Warsaw Convention for bodily injury (DVT) alleged to be caused by an "accident" during carriage by air.

Issues framed by the court:

• whether the onset of DVT can in principle be "an accident" causing bodily injury within article 17;
• whether an airline's omission to warn (in the absence of any established practice to warn) or the normal effects of a flight can constitute an "event" that is unexpected or unusual and external to the passenger;
• how to apply the established test in Air France v Saks and subsequent authorities.

Reasoning and outcome in brief: the House applied autonomous, purposive treaty interpretation and emphasised international uniformity of meaning. It endorsed the Saks formulation that an article 17 accident must be an unexpected or unusual event external to the passenger and stressed that the causative event, not the injury itself, must be the accident. On the agreed facts — normal aircraft operation and no unusual happening on board — the onset of DVT was the injury (or the first stage of it) and not an external accident. The court held that mere non-provision of warnings where there was no established industry or airline practice to warn did not convert the situation into an "accident". Comparative decisions (notably Povey v Qantas and United States and Canadian authorities) supported this conclusion. The House therefore dismissed the appeal. The court also noted the exclusivity of the Convention remedy: if article 17 does not provide relief, no alternative domestic remedy is available under the Convention regime.

Appeal dismissed. The House held that on the assumed facts (normal flight, no unusual or unexpected event on board, no established practice of warnings) the onset of DVT is not an "accident" within article 17 of the Warsaw Convention because the accident must be a cause of the injury, must be something external to the passenger and must be unexpected or unusual; mere cramped conditions or a carrier's omission to warn (absent an established practice) do not meet that standard.

Preliminary issue directed under a Group Litigation Order (May 2002) on an agreed specimen matrix. Decision below: Court of Appeal, In re Deep Vein Thrombosis and Air Travel Group Litigation [2004] QB 234 (and [2003] EWCA Civ 1005). Appeal to the House of Lords: [2005] UKHL 72 (this judgment).