English: The seat belt sign is still on
French: La consigne des ceintures est toujours allumée
The seat belt sign is still on after landing because you haven’t arrived at the gate yet and you need to make an announcement. Or during flight, you’re going through turbulence and you need to remind passengers that the seat belt sign is still on.
La consigne (des ceintures)=The sign (of the belts)
Remember that in French, in the context of an airplane, we can just say “la consigne” to mean “the seat belt sign.”
"La consigne (des ceintures) est allumée."
In French, there’s no easy way to say that something is “on” or “off”. The seat belt sign is a light that illuminates above each passenger on the airplane, so we literally say that the sign or light is illuminated: “allumé(e)”.
You can also say that the sign is “still” on. In French, we say “toujours”, which is also the word that means “always”.
Toujours allumé(e)=Always illuminated, Still illuminated