Pakistan International Airlines spokesman Mashood Tajwar said the airline had been unable to contact the pilot of flight PK709, despite repeated attempts.
Mr Tajwar said the control tower at Manchester Airport had received a call about a threat on board the plane and the advised the pilot to divert to its sister airport of Stansted.
More top news
A five-year-old boy whose surprise meeting with "Spiderman" became an online hit has died.
It's going to feel very cold in parts today, with temperatures between 3C and 6C before falling to as low as -6C in some areas overnight.
A son paid off his parents' mortgage for Christmas - reducing them to tears.