The European Court of Justice (ECJ) has affirmed the "obligation to provide care" incumbent upon Ryanair and other carriers following the eruption of Iceland's Eyjafjallajökull volcano in April 2010.
The low-cost carrier had refused to pay a bill of €1,130 ($1,530) submitted by an Irish passenger who became stranded in Portugal during the nine-day airspace closure.
Dismissing the airline's argument that the volcanic ash crisis was so unique it amounted to "separate category of 'particularly extraordinary' events beyond 'extraordinary circumstances'", the court said Ryanair must reimburse the passenger for her transport, meal and accommodation expenses.
It added that the burden of responsibility lies with airlines to "foresee costs linked to the fulfilment of their obligation to provide care", if necessary by increasing ticket prices.
Ryanair already charges all passengers what it calls the "€2 EU261 compensation levy" - a tongue-in-cheek reference to the 2004 ruling that enshrined passenger rights.
In reaching its conclusion, which upheld a March 2012 judgment by advocate general Yves Bot, the ECJ says: "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 can have access to essential goods and services throughout that period."
Ryanair says it "regrets" the ECJ's decision to hold carriers financially responsible for flight disruptions that are "clearly and unambiguously outside of an airline's control".
"Today's ruling by the European Court now makes the airlines the insurer of last resort even when in the majority of cases - such as ATC [air traffic control] delays or national strikes in Europe - these delays are entirely beyond an airline's control," it argues.
Although the "obligation to provide care" was upheld in all circumstances by the latest ruling, the ECJ reiterated that airlines are exempt from the "obligation to provide compensation" when delays arise from "extraordinary circumstances", including extreme weather.