Ryanair has warned that if a Spanish court ruling describing fees for reissuing boarding passes as illegal is upheld on appeal it will stop printing the passes.
The airline said passengers who show up for flights without a boarding pass will be unable to travel.
It also confirmed plans to vigorously contest the "bizarre and unlawful" decision of a Spanish court, which found it was wrong to impose "unfair" fees on passengers who failed to print out their own boarding cards.
Last week, Judge Barbara Maria Cordoba of the Barcelona commercial court said airlines and not passengers were obliged to issue boarding cards. She took the decision in a case brought by Dan Miro, a lawyer who objected to being charged €40 after he failed to print his boarding card before a flight.
"The normal practice over the years has been that the obligation to issue the boarding card has always fallen on the carrier," she ruled. "I declare unfair and therefore void the contractual clause in which Ryanair obliges the passenger to be the one who brings the printed boarding pass to travel or face a penalty of €40."
The airline said this morning it would base its appeal on the fact that its passengers agree at the time of booking that they will check-in online and print off their own boarding cards at least four hours prior to the scheduled departure of their flight.
It claimed that if a passenger arrived at an airport without their boarding card, then "they are not entitled to fly, and there is no obligation on Ryanair to provide them with replacements".
The carrier also insisted it was not open to the Barcelona commercial court "to redraft or alter the reasonable contractual terms already agreed between Ryanair and its passengers and which are readily observed by over 99 per cent of all Ryanair passengers who arrive at the airport with their boarding cards".
Ryanair's Stephen McNamara said the airline's systems appealed to passengers because it was "simple, efficient and agreed by each passenger at the time of booking".
He said that without these systems in place, Ryanair would have to employ "numerous handling agents at all airports to issue manual boarding cards for passengers who simply 'forgot' to bring their pre-printed boarding passes or who failed to comply with their original agreement to check-in online".
Mr McNamara said Ryanair could not understand how the court was in a position to "reinterpret a contractual agreement freely entered into" between it and its passenger "after the event".
He expressed confidence the ruling would be overturned on appeal and said that ahead of any such ruling the boarding card reissue fee would continue to be applied at all Ryanair airports for passengers arriving at airports without online boarding cards.
Mr McNamara warned if the ruling was upheld on appeal, it would cease offering a boarding pass reissue facility at airports and said that passengers who were not in possession of a valid boarding pass "will not be able to pass through security, and will be unable to travel. These passengers will then need to make a new booking for the next available flight at the current fare".