The military insists that it is keeping disruption to a minimum, as it stages a training exercise in the skies of London ahead of the Olympics.
Fighter jets and military helicopters will be operating above the capital, so that pilots become familiar with the airspace.
They will also be testing procedures used to intercept and communicate with aircraft breaching restricted airspace.
Air Vice-Marshal Stuart Atha, Air Component Commander for Olympics Air Security said:
“We have sought to limit the amount of flying to the minimum required to ensure that our Forces are ready for their important role delivering air security for the Olympics, balancing this against the need for us to reduce disturbance to a minimum.
"But we hope that people will understand the need for this very important training, and we thank them for their continued strong support.”
The Royal Navy's largest warship, HMS Ocean, sailed up the Thames today as the military stepped up security preparations for the Olympics.
The appearance of fighter jets in the skies over London will mark the start of an extraordinary Olympic test event.