There is no "specific" terror threat to the London 2012 Olympics, Defence Secretary Philip Hammond has said.
He said an elaborate military exercise carried out in London last week was to prepare for any threats that might arise in a dangerous world.
And he told the BBC's Andrew Marr show he now wanted the military to "fade into the background".
The exercise included tests of air defence missile systems at six sites across London, using dummy armaments.
Typhoon jets, based at RAF Northolt in west London, also took to the skies over south-east England with Lynx, Sea King and Puma helicopters.
Exercise Olympic Guardian, which ran until 10 May, also saw HMS Ocean sail to Greenwich in the capital.
Mr Hammond told Andrew Marr: "The idea now is that the military will fade into the background.
"We don't want to dominate these games.
"We want it to be a festival of sport and of culture, but the military will be there and we want people to know that the military are there in the background to provide ultimate reassurance."
He said the air defence operations would build on the Royal Air Force's existing defence of UK airspace.
"I am pleased to say there is no specific threat," he added.
Under the Air Security Plan, 30 miles (48km) of airspace surrounding the Olympic Park would become a restricted flying zone.
On the ground, the RAF will provide mobile ground radar systems, while the Army deploys air observers and high-velocity missiles.