European airlines suffered a setback Thursday in their efforts to overturn new rules forcing them to pay more compensation to passengers whose flights are overbooked, delayed or canceled.

A senior adviser to the European Union's high court ruled the regulations are in line with E.U. law.

Advocate General Leendert Geelhoed recommended the European Court of Justice dismiss the complaints brought by the International Air Transport Association and the European Low Fares Airline Association.

The new rules came into force in February. They force airlines to pay passengers up to $745 if they are bumped off a flight, double the previous limit.

The airlines say the rules will cost them hundreds of millions of dollars. In their complaint to the Luxembourg-based court, they claim the rules infringe on international agreements, breach legal principles and give unfair advantages to other forms of transport.

Geelhoed's opinion is not binding on the court, but final rulings follow the advocate general's recommendations in about 80 percent of cases. The ruling is expected to take several months.

In a statement, the court said Geelhoed judged the rules are "proportionate to the inconvenience suffered by the passengers and therefore fair."

The rules offer similar compensation if a flight is canceled and the airline is responsible.

Delays of two to four hours will require airlines to serve snacks or full meals, while delays over five hours entitle passengers to a refund and a hotel room if necessary. Return flights must be offered if the journey is no longer necessary, for example if a business meeting is missed.

The International Air Transport Association estimates that new legislation will cost $745 million this year. Low cost airlines have been particularly critical, claiming the compensation is often much higher than the cost of their tickets.

Geelhoed rejected their claim of discrimination.

"A decision by an airline to pursue a low-fares model should not result in them being privileged under the law," he said.