The High Court has considered once more the thorny issue of what constitutes an “accident” for the purposes of the Montreal Convention and has provided at least some clarification.

The case

Mr Arthern was a passenger on Ryanair’s flight from Manchester to Hamburg. It was winter; the ground outside the aircraft was wet, and the aeroplane had to be de-iced. A short time into the flight, Mr Arthern headed to the toilet and slipped near the toilet door, sustaining injury. His unchallenged evidence was that he had slipped on a large amount of fluid on the floor, which may have been water, or a combination of water and de-icer, trailed into the aeroplane on the shoes of passengers. He contended that this was an “accident”, for the purposes of the Convention. The judge at first instance concluded that it was not. On appeal, the High Court declined to interfere with that conclusion.

The Montreal Convention, Article 17(1)

The Convention applies to the international carriage of persons, baggage or cargo by aircraft for reward. Article 17(1) states:

“The carrier is liable for damage sustained in case of death or bodily injury of a passenger upon condition only that the accident which caused the death or injury took place on board the aircraft or in the course of any of the operations of embarking or disembarking.”

It provides an entirely different scheme for the assessment of liability in relation to personal injury claims than that which applies away from aircraft. It is not necessary to prove negligence. The claimant must simply prove that the injury was caused by an “accident”. Even if the defendant was negligent, and that negligence was causative of the accident, unless the claimant can establish that the injury was caused by an “accident” within the meaning of the Convention, the claim will fail.

Precisely what constitutes an “accident” for these purposes is, however, a more slippery issue.

Case Law

The seminal authority on what constitutes an “accident” under Article 17(1) is Air France v Saks 470 US 392 (1985). Liability will arise “only if a passenger’s injury is caused by an unexplained or unusual event or happening that is external to the passenger.” An event which is no more than the normal operation of the aircraft in normal conditions cannot constitute an accident.

As established in the Deep Vein Thrombosis Litigation [2005] UKHL 72, the question of whether an event was “unusual” or “unexpected” is to be assessed from the viewpoint of the passenger, specifically (Moore v British Airways PLC No. 21-1037 (1st Cir. 2022)) the ordinary, reasonable, passenger. It is a subjective, not objective, test.

Application in this case

In Richard Arthern v Ryanair DAC [2023] EWHC 46 (KB), the judge at first instance considered that a reasonable passenger, knowing it was an icy day, would not find the presence of slippery fluid on the floor close to where people entered the aeroplane to be unusual or unexpected. In the circumstances, it was not an “accident”, and the claim failed.

Ryanair’s evidence consisted of written evidence from a manager, commenting on the accident report completed by one of the cabin crew. It was limited to commenting on what would “normally” happen in wet conditions (that transferred fluid is normally very limited and dries quickly; it was not normal for crew to clean the floor in such circumstances). She was not called to give oral evidence for reasons, the court was told, of proportionality.

On appeal to the High Court, Mr Arthern argued that the judge had failed to properly apply the law to the facts of the case. The evidence indicated that there was an unusually large amount of fluid. The defendant’s evidence had been that moisture tracked into the cabin in wet conditions usually dried very quickly. It followed that the presence of a large amount of fluid must by implication be unusual or unexpected.

Not necessarily, found the High Court. Having heard all of the evidence, the judge was entitled to conclude that it would not be unusual or unexpected, from the viewpoint of the reasonable passenger, that a large amount of liquid was tracked into the cabin by numerous passengers. There were no grounds to interfere with her reasoning, and the court was not prepared to substitute its own judgment of what was “unusual” or “unexpected.” The appeal was dismissed.


The case is interesting for a number of reasons. Firstly, it provides a helpful review of the key authorities on the scope of “accident” for the purposes of Article 17(1). Secondly, it is notable, and perhaps surprising, that Ryanair succeeded despite choosing not to adduce any direct witness evidence on the conditions at the time or any evidence about their operating procedures in icy conditions. Had this been a negligence case, they would clearly have struggled, but it was not. Thirdly, it illustrates that the decision as to whether an event is “unusual” or “unexpected” can be a fine one.

The case of Carmelo Labbadia v Alitalia [2019] EWHC 2103 (Admin) was considered. In that case (see our previous Law-Now here), the claimant had slipped and fallen down the aircraft steps when disembarking in Milan in snowy conditions. The steps were uncovered. This was in breach of the airport’s operating manual and therefore not “normal operation of the aircraft.” The factual circumstances (a slip owing to the effect of weather conditions on the aircraft’s walkways) are not dissimilar from Arthern. However, it was found in Labbadia that the event was unexpected and unforeseen by the claimant “because he had no reason to expect that the stairs would be slippery from compacted snow.” The event was also external to the claimant. Consequently, all criteria for an accident were met.

It is perhaps important to recognise that the High Court did not find, and did not need to find, that the judge’s conclusion was plainly right, merely that it was a reasonable one and certainly not so contrary to the evidence that it ought to be overturned. A different judge may have reached a different conclusion, applying the same principles to the same factual findings. The case nevertheless provides further, helpful, guidance on the application of recognised legal principles when determining whether an “accident” has occurred.