The transport chief tasked with flying 500,000 visitors to Britain for the Olympics has admitted: "It's quite a challenge."

The London terminal control general manager for National Air Traffic Services (Nats), Paul Haskins, will be responsible for organising thousands of aircraft jetting in and out of the capital for the summer showpiece - and avoiding a catastrophic mid-air collision.

He has cancelled leave for 360 air traffic controllers as Nats prepares to deal with 4,000 extra flights destined for airports serving the Games.

Staff have undergone special radar training to monitor newly-restricted airspace around London and cope with 700 extra airliners and more than 3,000 executive jets flying in and out of South East airports over three weeks before, during and after the Olympics.

The zone surrounding London from which private planes, hot air balloons and microlights are banned will increase by up to 30 miles in all directions to cut the chance of a mid-air crash between a private plane and a jumbo jet packed with sports fans.

The month-long restrictions, which come into force on July 16, cover as far north as Stansted, south to Weymouth, east to the Thames estuary and west to Oxford.

Military chiefs fear pleasure pilots could accidentally stray across the widened boundaries, leaving air controllers unclear as to whether it is a genuine mistake or a hijacked plane destined for the Olympic Stadium in Stratford, east London.

"During the Olympics if you start infringing London's airspace and you're heading towards one of the key stadiums, the Ministry of Defence is likely to see you as a threat," Mr Haskins said in an interview with the Press Association.

"The Civil Aviation Authority is responsible for uncontrolled airspace.

"We have done a lot of work with them in terms of education because we don't want light aircraft and microlights getting confused about what is and isn't controlled airspace and wandering into an air lane we wouldn't want them in."

Experts at Nats, responsible for airspace used by commercial airliners, will be the first to know if a plane enters restricted skies, triggering automatic responses which could lead to the RAF launching its Quick Reaction Alert Typhoons to intercept suspect aircraft.

Two fighters were launched earlier this month when a private helicopter failed to respond to warnings, leading to one Typhoon breaking the sound barrier over central England and creating a sonic boom heard by millions.

Mr Haskins said: "Our role is to accommodate the RAF in whatever it deems appropriate in terms of risk assessment and deciding what's a threat.

"If a national security event is declared through the Government and RAF, civilian air traffic is moved out of the way."

He added military commanders would not have "the luxury" of knowing whether an unidentified plane was a small plane with a lost pilot or a hijacked jet with a terrorist intent on mass murder at the controls.

"The MoD just knows there is an aircraft in airspace it shouldn't be, heading towards a populated area," said Mr Haskins.

"They will have to do a risk assessment and you might find there is a security response to that flight because they are trying to work out if it is a threat."

Another issue which could affect the Games is the potential for queues at airports' border controls, which could have a knock-on effect for flights meaning delays and disruption,

Earlier this month MPs revealed their concerns that Heathrow might struggle to cope with increased demand, sparking fears of long waits for immigration checks, which could lead to passengers being kept on planes after landing, clogging up aircraft parking spaces and creating congestion on aprons, forcing officials to "stack" jets in the sky.

Mr Haskins said planes could be held at departing airports to avoid putting too much stress on destination airports and said it was unlikely controllers would need to put jets into holding patterns.

He said systems were in place so Nats could warn airlines of congestion, meaning pilots of London-bound lanes could be ordered not to take off from European airports - minimising pressure at South East terminals.

"We have regular telephone conferences with airports throughout the day where we are looking at forecast demand for the next three to four hours," he said.

"They advise us in terms of what they can handle and we will regulate the airspace and flows of aircraft to meet whatever the airport has declared its capacity to be."

He added: "We don't get into a situation where they ring us up and say, 'No more, thank you very much.'"

As well as the extra planes bringing fans, Olympics officials, athletes and media to the capital, three aircraft will hover over Games' venues providing television footage of events like the marathon and road cycling, with another three nearby.

And the demands of American television have placed a rather more unusual burden on airspace regulation so one channel can bring its audience a bird's-eye view of the Olympic Park.

Mr Haskins said: "The broadcaster NBC is chartering an airship for the whole of the Games from where it will present its coverage."