A United Airlines flight from Newark to Palma de Mallorca was diverted back to Newark after a passenger's Bluetooth device named 'BOMB' triggered a security alert. The crew issued warnings and eventually declared an emergency, landing the plane back in Newark. The device was later found to belong to a 16-year-old passenger and was deemed not to be a threat. The incident highlights the airline's strict security protocols and the potential consequences of perceived threats on flights.