Can you cite an instance where a bomb warning to a flight was not a hoax ?
PaperTiger, really good question, but kinda misses the point ... unless you want to argue that since there has been none, that they can then be ignored. Which then raises the issue of why aircraft are diverted and quarantined rather than just continue to their destination.
(By the way, I do think there have been a couple of bomb warnings prior to aircaft losses in the distant past ... an insurance scam comes faintly to mind, but I cannot be sure).