A more complete quotation from an online screenplay clarifies it a little:
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.
-- 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.