RyanAir has backtracked on its decision to only provide customers disrupted by the ash cloud with compensation equal to the value of their original ticket.
The low-cost airline had said that it would not be offering its passengers "reasonable receipted expenses", which is required under EU261 regulations.
Instead it said it would refund the original cost of the ticket, arguing that the airspace closure was out of the control of airlines.
However, this decision has now been reversed and passengers will be able to claim for some of the costs they incurred due to the disruption.
RyanAir boss Michael O’Leary said: "The events of the last seven days, under which Europe’s airlines were prevented from flying by the closure of European airspace highlight how absurd and discriminatory the EU261 regulations are towards Europe’s airlines."
He claimed that the same rules on reimbursement are not applied to ferry, coach and train operators.
Mr O’Leary added that RyanAir will continue to campaign to have the regulations changed.
The airline has also said that it will be waiving check-in and baggage fees over the next few days.