Al Pacino doesn't use the word "sillage" when he comments about the flight attendant: "Well, she’s wearing Floris. That’s an English Cologne..."
I found the term explained in the "Perfume Notes" section of Bois de Jasmin:
Sillage (pronounced as see-yazh) is a term used to describe a scented trail left by the fragrance wearer. It comes from the French word for “wake,” as in the trail left in the sky by an airplane or on the water by a boat. Sillage defines how fragrance diffuses around the wearer, and a strong sillage means that a fragrance projects well. Sillage has nothing to do with the richness of the composition, however, but rather with the diffusive nature of the materials that go into it. For instance, hedione, fresh floral notes and some types of musk are extremely diffusive and radiant, while retaining an airy, light character.A hat tip to reader Jeff Kozoris, who remembered encountering the term when I posted some quite interesting facts about language.
Fragrances with a strong sillage include such rich compositions like Guerlain L’Heure Bleue, Lancôme Trésor, and Christian Dior Poison as well as light, ethereal blends like Bulgari Eau Parfumée au Thé Vert and Christian Dior Eau Sauvage. Conversely, minimal sillage fragances are ones that stay close to the skin and create a more intimate scented aura.