Olympic Park Aerial View

Aerial view of a temporary airfield on Wanstead Flats, London, which will be used as a base for military helicopters during the Olympic games, London, Thursday, July 12, 2012. The opening ceremony for the London Olympics is July 27. (AP Photo/PA, Dominic Lipinski)

Aerial view of the Olympic Park, in Stratford, east London, showing the Olympic Velodrome, top, and the BMX track in London, Thursday, July 12, 2012. The opening ceremony for the London Olympics is July 27. (AP Photo/PA, Dominic Lipinski)

The Olympic Stadium, foreground, is backdropped by a view of central London, Thursday, July 12, 2012. (AP Photo/PA, Dominic Lipinski)

Aerial view of the Olympic Park, in Stratford, east London, showing the Olympic Stadium and a view of central London, including Canary Wharf, London, Thursday, July 12, 2012. The opening ceremony for the London Olympics is July 27. (AP Photo/PA, Dominic Lipinski)

Aerial view of the Olympic Park, in Stratford, east London, showing the Olympic BMX track, London, Thursday, July 12, 2012. The opening ceremony for the London Olympics is July 27. (AP Photo/PA, Dominic Lipinski)

Aerial view of the William Girling Reservoir, in Enfield, London, which will be a site for surface to air missiles during the Olympic games, London, Thursday July 12, 2012. The opening ceremony for the London Olympics is July 27. (AP Photo/PA, Dominic Lipinski)

An aerial view shows the construction of the Olympic Beach Volleyball arena, on Horseguards Parade, in London, Thursday July 12, 2012. The opening ceremony for the London Olympics is July 27. (AP Photo/PA, Dominic Lipinski)

An aerial view shows the construction of the Olympic Beach Volleyball arena, on Horseguards Parade, in London, Thursday July 12, 2012. The opening ceremony for the London Olympics is July 27. (AP Photo/PA, Dominic Lipinski)

An aerial view of the Olympic Park, in Stratford, east London, showing the Olympic Stadium and the ArcelorMittal Orbit sculpture, at left, in London, Thursday July 12, 2012. The opening ceremony for the London Olympics is July 27. (AP Photo/Dominic Lipinski, PA)

An aerial view of the Olympic Park, in Stratford, east London, shows preparations for the opening ceremony inside the Olympic Stadium, London, Thursday July 12, 2012. The opening ceremony for the London Olympics is July 27. (AP Photo/PA, Dominic Lipinski)

An aerial view of the Olympic Park, in Stratford, east London, shows preparations for the opening ceremony inside the Olympic Stadium, London, Thursday July 12, 2012. The opening ceremony for the London Olympics is July 27. (AP Photo/PA, Dominic Lipinski)