An unprecedented security lockdown of UK airspace over Olympic venues to prevent a 9/11-style attack will push British aviation companies to the brink of bankruptcy, according to the industry.

Aircraft that fail to comply with a no-fly zone over the capital and vast swathes of south-east England face being shot down by military Apache helicopters.

A month-long clampdown beginning next July will restrict all but essential flights over the capital to prevent any aircraft, including microlights and hang-gliders, from being used in a terrorist attack on Games venues or other disturbances.

Similar restrictions will apply over Weymouth and Portland, where sailing events will be staged, and over the football stadiums in Coventry, Cardiff, Manchester, Glasgow and Newcastle. Aircraft entering restricted airspace will require permission from RAF wing commanders seconded to the Metropolitan Police or face being shot down by the military.