"death flight" means: A form of extrajudicial killing done by military, in which victims are dropped to their death from airplanes or helicopters into oceans, lar.... This is a fairly neutral word with no inherent risk attached. There is no real cause for parental concern; it is descriptive vocabulary rather than something dangerous. If your child uses it, context will usually make the meaning clear. A brief, curious question about where they heard it is generally enough to know whether to follow up.