A total of 116 people are aboard a missing plane due to land in Algiers, Spanish airline Swiftair says.
The airline said there was currently no contact with the aircraft, which is thought to contain 110 passengers and six crew.
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Among those expected to attend the ceremony will be former US President Bill Clinton and ex-Northern Ireland first minister Peter Robinson.
Five people have been killed and 40 injured after a car and knife attack in London on Wednesday.
A wet, wintry night in places with rain and hill snow slow to move away from southern Scotland and northern England.