To travel, every passenger must be in possession of a valid ID.
Some destinations may even require that your ID be valid for several months after your trip.
Extension of the validity of a French national identity card:
On January 1, 2014, the validity of the French national identity card (for French citizens and under certain conditions) was extended from 10 to 15 years for adults (over 18 years of age), while cards issued before this date are automatically valid for an additional 5 years.
Please note that this extension does not apply to those who were minors when their identity card was issued.
For more information, please visit the website of the French Ministry of Foreign Affairs and International Development.