French President Nicolas Sarkozy and his girlfriend Carla Bruni are suing low-cost airline Ryanair over a picture of the couple it used in an advert.
The couple say the image was used without their consent
The photo shows a thought bubble coming from Ms Bruni, saying: "With Ryanair, all my family can attend my wedding."
The former model is seeking 500,000 euros ($743,000; £373,000) - the amount she says her photo normally costs.
Ryanair has apologised for using the couple's image without their consent, but insists it meant no offence.
"It was a humorous comment on a matter of great public interest," a Ryanair spokeswoman in Dublin told Reuters news agency.
The picture features in an ad for 100,000 cut-price fares, published on Monday by the daily Le Parisien.
Mr Sarkozy, 53, and Ms Bruni, 40, are filing separate suits against the Irish airline.
The couple's lawyer, Thierry Herzog, is quoted by AFP news agency as saying her damage claim was based on the fact that "the average cost for using her image for visual advertising on French territory was in the region of 500,000 euros".
Mr Sarkozy is seeking a symbolic one euro in damages.
Both cases are being heard in a Paris court on Thursday.
The couple began their relationship late last year, after the president's divorce. Their relationship has been front-page news worldwide.
Mr Sarkozy has hinted that they would marry, but no date has been announced.