Passengers stranded after a plane landed at the wrong airport may not have been offered compensation they were entitled to under EU law.
The plane landed at an Army base five miles away
Last month a Ryanair flight from Liverpool to Londonderry landed at Ballykelly airstrip instead of City of Derry airport.
Passengers were left stranded at City of Derry when the plane's return flight to Liverpool was cancelled.
Ryanair said it had offered alternative transport arrangements.
Watchdog groups on both sides of the Irish border said the passengers were entitled to payments of about £170 each.
Tina Leonard of the European Consumer Centre in Dublin said she believed Ryanair "did not handle it very well".
"They certainly did not handle it as they are obliged to," she said.
"Under European regulation 261 - which deals with air passenger rights - says when a flight is cancelled there is the refund of the ticket or the re-routing... and that was offered.
"There is also duty of care if you are waiting around for the next flight for a couple of hours.
"I don't know if the passengers who were bussed to Dublin for a later flight were given meals, refreshments and telephone calls - but they certainly should have been.
"But the crucial addition, the entitlement that we all have if the flight is cancelled... then you are also entitled to financial compensation."
In a statement, Ryanair said: "We were forced to cancel the return flight to Liverpool as the airport was in Ballykelly airport.
"In the circumstances, Ryanair complied fully with its contractual obligation as passengers were offered alternative transportation to Liverpool via Dublin with a coach service from Derry airport to Dublin."