Aer Lingus has refunded only 7,000 of the 70,000 passengers due payments after they were affected by the recent Icelandic ash cloud. Customers may have to wait up to three months to be reimbursed as the backlog in claim applications grows.

Thousands of travellers are still out of pocket as the claims continue to flood in. The airline confirmed it is continuing to receive requests for reimbursement on a daily basis.

Fine Gael TD Fergus O'Dowd says despite current financial difficulties in the airlines, both Aer Lingus and Ryanair should "refund the customers immediately."

"It is understandable that the airlines are in financial difficulty but the customer must come first. The airlines are obliged to cover the costs, and they should not drag their heels on this."

A spokeswoman for Aer Lingus said they have taken measures to ensure travellers receive their refund quickly.

"We are getting through them as fast as we can, and have taken extra staff on board. The disruption caused to aviation due to the volcanic eruption in Iceland has been unprecedented in scale. As a result, we have received a very large volume of requests for refunds and reimbursement claims ... We have a dedicated team working to ensure that claims are processed as quickly as possible."

By EU regulations, refunds should be sent to customers within seven days.

"There are guidelines under the European Code of Practice, and this needs to be adhered to and there's no two ways about it," says O'Dowd.

Aer Lingus says it is going through claims in order of when it receives them.

"All customers who submit a claim receive an acknowledgment from our customer relations team. Claims are processed in a chronological order," said a spokeswoman.

Meanwhile, the Aviation Regulator, who will intervene in any dispute over claims, says passengers should submit genuine expenses along with the legitimate paperwork to support their claim in the event of a dispute.