A spokesman for Stansted Airport said passengers were being taken off the plane.
"They will be taken to a reception centre in the airport where police may wish to interview them about what they have seen. At some point police and the airline will arrange for their onward transportation to Manchester."
A Manchester Airport spokesman said:
"The plane - flight number PK709 - was travelling from Lahore and had 297 passengers on board. For further information for friends or family who were due to meet the flight at Manchester please call 0800 140 4007.