A law firm acting for one of the survivors of the Cork airport crash last week has said the Manx 2 airline should not renege on its responsibilities.
Mark Dickens from Watford survived the plane crash in which six people died.
His lawyers, Stewarts Law, have written to Manx2, seeking details of insurance provison and an advance payment for Mr Dickens of more than £15,000.
Manx 2's solicitors said the airline was not responsible for such claims.
In a letter to Stewarts Law, Appleby Solicitors for Manx2 said the airline had acted as "ticket provider or booking office" and that according to the terms and conditions of Mr Dickens' ticket purchase the carrier was Flightline BCN and his contract was with them.
It added that Mr Dickens' claim should be directed to that company, which is based at Barcelona in Spain.
It said the advance payment of £15,497 was "not payable by our client for this reason".
Stewarts Law is seeking the payment to cover costs of humanitarian support to Mr Dickens, who was to be transported by aircraft to the UK for medical care on Thursday from Cork University Hospital.
Head of the aviation department at the law firm, James Healy-Pratt, has rejected the response by Manx2's solicitors.
He said that under the Montreal Convention and European regulations "a passenger that suffers death or injury has the right to seek compensation from either the contracting carrier or the actual carrier".
"Having done this for 20 years, this is the first time I have seen this situation," he said.
"I would expect Manx2 to step up and take responsibility and sort it out for all the families.
"They promised support last week and when asked for support this week, they promptly backed away and said it wasn't their problem."
In a statement, the chairman of Manx2, Noel Hayes, said that under the terms of the contract, the airline had chartered the aircraft involved in the Cork crash from Flightline BCN.
He said that under the European Air Operators Certificate, such carriers maintained full insurance provision.
"These carriers maintain full insurance at or above Civil Aviation Authority (CAA) minimum levels," the statement added.
"This kind of arrangement is common in the aviation industry and ensures the necessary cover for passengers and their families in the event of such awful circumstances."
Mr Hayes said Manx2 continued "to extend our deepest sympathy to the families of those who lost their lives in Cork and to those who are still recovering from this terrible incident".
A spokesperson for Flightline BCN in Spain was unavailable for comment.