Police have arrested three men on a plane at London's Heathrow Airport on suspicion of making a bomb threat. Armed officers boarded the Dubai-bound Emirates flight after verbal threats were made to air crew. The Metropolitan Police said the three men, aged aged 58, 48 and 36, were in police custody. They have been arrested on suspicion of making a bomb threat, police said.<br/><br/>Police searched the aircraft, which had 331 passengers on board, and it is learnt that no dangerous substances have been found. <br/><br/>The incident comes amid heightened tension at airports across the world following an unsuccessful attempt to bomb an airliner on Christmas Day.