A note was handed to the pilot of the plane who then reported the possible device on board, according to Manchester Evening News reports.
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The referendum story is rapidly heading south. Scottish voters were promised more power - now English and Welsh voters ask "what about us?"
The Scottish independence referendum was threatening to turn into a huge boost for separatist movements in many countries in Europe.
A sigh of relief across Westminster and a crushing sense of disappointment for 45% of Scotland, but Yes campaign could not have done more.