Narrator: Home was a condo on the 15th floor of a filing cabinet for widows and young professionals. The walls were solid concrete. A foot of concrete's important when your next-door neighbor has to watch game shows at full volume. Or when a blast of debris that used to be your personal effects blows out of your windows and sails flaming into the night.
What does "sails flaming" mean? I know sailing boat, how can you sail flames?
Source: Fight Club (1999)
A more complete quotation from an online screenplay clarifies it a little:
JACK (V.O.) The walls were solid concrete. A foot of concrete is important when your next-door neighbor lets her hearing aid go and has to watch game shows at full blast ...
The taxi turns a corner and Jack sees the front of the building. A diffuse CLOUD of SMOKE wafts away from a BLOWN-OUT SECTION on the fifteenth floor. FIRETRUCKS, POLICECARS and a MOB are all crowded around the lobby area.
JACK (V.O.) -- Or when a volcanic blast of burning gas and debris that used to be your furniture and personal effects blows out your floor-to-ceiling window and sails down flaming to leave just your condo -- only yours -- a gutted, charred concrete hole in the cliffside of the building.
The sense is that those materials sail down, because there has been an explosion in the apartment, and some of the contents thrown out the windows are on fire, that is, they are in flames, or flaming.
It might be easier to imagine commas both before and after the word “flaming”. It is a descriptive word that can be omitted without changing the meaning of the sentence. The debris was sailing (flying) out of the window through a force that it did not generate. Simultaneously, the debris can be described as flaming or being in flames. Said debris just happened to formerly be the characters personal belongings.
