Ryanair today lost the latest round in its legal battle to avoid paying for hotels, meals and drinks for passengers disrupted by delayed flights during the Icelandic volcano eruption in 2010.
EU rules oblige airlines to provide passenger care - but not compensation - when flights are cancelled by "extraordinary circumstances" beyond their control.
But Ryanair argues that the closure of airspace following the eruption of the Eyjafjallajökull volcano was so extraordinary that the rules should not apply.
Today, in a legal "opinion", an Advocate General of the European Court of Justice in Luxembourg declared: "In everyday language, the term 'extraordinary circumstances' refers to all circumstances over which the air carrier has no control: an event which is not inherent in the normal exercise of the activity of the air carrier concerned and is beyond the actual control of that carrier on account of its nature or origin.
"In the view of the Advocate General, all events which meet that description are bracketed together under a single notion, leaving no room for a separate category of 'particularly extraordinary' events which would fully release the air carrier from its obligations."
The "opinion" will now be considered by the full court which will deliver a final verdict later this year. The view of the Advocate General is followed in about 80% of cases.
The legal battle began in the Dublin Metropolitan District Court, which is hearing a dispute between Ryanair and passenger Denise McDonagh, whose flight from Faro to Dublin was cancelled by the volcanic ash cloud which closed most northern European airspace between April 15 and 23 2010.
In his legal "opinion" today, Advocate General Yves Bot said Ms McDonagh's scheduled April 17 flight was one of Ryanair's cancelled services, which did not resume until April 22. Ms McDonagh was finally able to return to Ireland on 24 April.
The Advocate General said: "According to Ms McDonagh, Ryanair did not provide her with the necessary assistance and it is required to pay her around 1,130 euro (£940) by way of compensation or damages to cover the costs which she incurred for meals, refreshments, accommodation and transport."
The Dublin court had asked the Luxembourg court whether the closure of airspace owing to the eruption of a volcano is covered by the notion of "extraordinary circumstances" in the EU rules, obliging airlines to provide passenger care, or whether it falls "within a category of events above and beyond extraordinary circumstances, possibly releasing the carrier from that obligation".
The Advocate General said the notion of "extraordinary circumstances" was not defined in EU law, and its meaning had to be decided "in accordance with its usual meaning in everyday language".
He said his assessment - that there is no higher category than "extraordinary" - was borne out by the intention of the rules to ensure a high level of passenger protection and by the context, "which relates to the particular vulnerability of passengers who find themselves stranded at an airport on account of extraordinary circumstances".
"Extraordinary circumstances" beyond the control of airlines did remove the obligation to pay passengers compensation for cancelled flights, but the requirement to provide care remained - without a cash or time limit.
"The provision of care is particularly important in the case of extraordinary circumstances which persist over a long time," said the Advocate General.
"It is precisely in situations where the waiting period occasioned by the cancellation of a flight is particularly lengthy that it is necessary to ensure that an air passenger whose flight has been cancelled can have access to essential goods and services throughout that period.
"A limitation of the obligation to provide care would in some measure deprive the EU legislation of its effectiveness, since after a few days the air passengers concerned would be abandoned to their fate."
He summed up: "To meet the immediate needs of such passengers, the air carrier must provide, free of charge, meals and refreshments in a reasonable relation to the waiting time and, where necessary, hotel accommodation and transport between the airport and the place of accommodation, and must place at their disposal means of communicating with third parties.
"The air carrier is required to meet that obligation even where the cancellation of the flight has been caused by extraordinary circumstances, that is to say, circumstances which could not have been avoided even if all reasonable measures had been taken."