Fireflybob.
Any threat would initiate a Red Alert and subsequent interception etc.
Do you really think that say, a person would go to all the trouble of obtaining the materials, constructing a device, being careful not to leave any evidence, DNA, credit card details of course. Smuggle it onto an aircraft, then scrawl a message in an in- flight magazine that may or may not be read on that particular page, claiming there's a device on board.
There's probably loads of such messages flying around in magazines at this very moment, and if I found one, I'd destroy it ( and not by setting fire to it).