A Brussels court has upheld a complaint by Belgian national airline Sabena against an advertising campaign by Ryanair.
The court ruling held the campaign was misleading and offensive and ordered Ryanair to discontinue the adverts immediately.
In addition, the court ordered the full page publication of the court order in four national newspapers and on Ryanair's website under the banner 'Sabena versus Ryanair'.
"We welcome comparative publicity. But this has to be within the boundaries of the Belgian law," said Mr Patrick du Bois, Sabena's secretary general.
"Strategies that mislead the public at large or offend our passengers and our personnel are not to be allowed."
Ryanair ran a series of advertisements comparing its prices with Sabena after it located its mainland Europe hub in the Belgian city of Charleroi, 40 miles south of Brussels, where Sabena has its hub. That move in April made Ryanair a direct competitor with Sabena on several routes.
Ryanair said it would comply with the court ruling that its advertising should include details of prices and comparative quality of services.
"We are really, really sorry Sabena," said a statement from Ryanair Chief Executive Mr Michael O'Leary. "We promise to include details of our prices and the quality of our services in all our future advertisements"
The Ryanair statement then listed price differences indicating its fares were up to 89 per cent cheaper than those on Sabena.
"We are delighted that our 100,000 passengers per month have not been confused by our forgetting to include in our ads just how much lower our fares are and how much better our quality of service is compared with Sabena," Mr O'Leary said.
AP