AUDIO: Another 27 flights across Europe hit by bomb threats, but no explosives found - ABC News & Headlines – Australian Broadcasting Corporation

Passengers check their flights in Rome after a flight from Dublin to Rome was diverted to France. (AP: Gregorio Borgia)

Dozens more flights across Europe have been caught up in bomb threats, just days after a similar wave of hoaxes.

Every time one of these planes has landed, nothing's been found on board.

So who's sending the threats, and what do they want?

Sarah Morice spoke to Julian Bray, an aviation security expert in the UK, about what's behind the wave of bomb hoaxes on flights.