Police confirm one of the 12 was stopped at Heathrow and a house in Luton was searched.
Pilot Killed In Airshow Crash
A pilot's died after his plane crashed at an airshow in Bedfordshire being watched by 600 people.
The crash happened at Old Warden Aerodrome, near Biggleswade, which is home to the Shuttleworth Collection of vintage aircraft, as 600 people attended a military pageant show.
The crash happened at 9.45am on Sunday 1 July 2012.
Bedfordshire Police worked with Bedfordshire and Luton Fire and Rescue Service, the East of England Ambulance Service and the aerodrome’s own fire service to help the 46-year-old pilot but he was pronounced dead soon afterwards.
The incident is being investigated by the Air Accident Investigation Branch.
The collection confirmed in a statement on its website that an aircraft had experienced difficulties and crashed.
"Today's planned air show has been cancelled to allow accident investigators to assess the scene.
"We would like to thank both on-site and external emergency crews for their prompt reaction."
A spokesman for the Air Accidents Investigation Branch said that the aircraft involved was a DH 53 vintage aircraft.
"A team of inspectors have been despatched to the site, to start an investigation which will determine the circumstances behind the accident," he added.
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