Ryanair has admitted defeat in its takeover bid for Aer Lingus but vowed to fight the decision in the courts.
The European Commission told the airline that the 694 million euro (£596.7 million) buyout plan would be rejected.
The low-cost carrier claimed European chiefs were holding it to much higher standards than any other EU airline.
Ryanair spokesman Robin Kiely said: "It appears clear from this morning's meeting that no matter what remedies Ryanair offered, we were not going to get a fair hearing and were going to be prohibited regardless of competition rules."
Ryanair boss Michael O'Leary has predicted that travellers will need to pay more in fares after today's ruling on passenger compensation by the European Court.
ITV News Consumer Editor Chris Choi reports.
The Which? consumer group said there is no reason airlines should increase fares in the light of the European Court of Justice ash cloud ruling.
Today's ruling by the European Court of Justice simply confirms the existing situation relating to the 2010 ash cloud travel disruption - that airlines should reimburse passengers for reasonable costs, including accommodation food and transport.
Airlines already account for compensation in their ticket costs, so there should be no reason for any airline to increase their prices as a result.
The European Court of Justice has ruled that Ryanair should have compensated passengers whose flights were cancelled because of volcanic ash in 2010.
Twitter users have been reacting to the ruling today:
Michael O'Leary quick enough to take your money... then threatens to hike up fares when he doesn't get his own way..
Gillian Edwards, of travel trade association Abta, has said that today’s ruling by the EU’s top court means Ryanair cannot “wriggle out” of its obligations to customers.
Today's ruling doesn't change passengers' rights but it does show that Ryanair has the same obligations to its customers as any other airline and can't wriggle out of its responsibilities.
Bob Atkinson, of travelsupermarket.com, has urged passengers to contact airlines as soon as they are delayed to avoid requiring court action.
Ryanair boss Mike O'Leary said today's decision by the European Court was "crazy" and would result in increased airline prices for passengers across Europe. He told Sky News:
Why do we have to take responsibility for delays caused by others? Airlines will be sued by passengers for things that are beyond our control. This is another crazy decision from the EU court. We can't be responsible for providing compensation for the world and his mothers, for situations out of our control.
Today's ruling the EU court on the duty of care owed to passengers by airlines is significant. Our guide to how it could affect you.Read the full story ›
The UK Civil Aviation Authority has today reiterated its advice to passengers affected by flight delays and cancellations
It follows rulings in both the UK and European courts in favour of compensation to passengers whose flights were delayed or cancelled.
These regulations are in place to protect people when things go wrong with their flights. Anyone with concerns that they are not being treated correctly by their airline can contact the CAA for advice or to make a complaint.