THE screen of an air force flight simulator flickers on, revealing a panorama of the Central Business District and its towering skyscrapers.

Soon, a Black Knight flies about 900m above the roof of the 280m-tall UOB Plaza before swooping down towards Marina Bay and whizzing past another Black Knight.

It is a simulation that has now become a routine.

The six ace Black Knight pilots from the Republic of Singapore Air Force have run through such scenarios about 20 times between May and last month.

The pilots have also practised flying their F-16C Fighting Falcons over Marina Bay and the islands at the southern tip of Singapore, such as Pulau Sudong and Pulau Pawai.

The preparations will culminate in a heart-stopping routine of aerial acrobatics at next month's National Day Parade (NDP).

By the time they take to the skies on Aug 9, the pilots would have clocked about 120 hours of flying time practising for the big show.

Their objective: to wow the 300,000 people expected to show up at Marina Bay - and to do so safely, said Colonel Ho Foo Sing, the NDP's chairman of air participation.

The Black Knights, who fly at a speed of 13km a minute, will have no room for error. Although their manoeuvres take place only over the water, their flight paths will take them over the downtown core.

Flying over a built-up area leaves pilots with less space to perform their manoeuvres, said Col Ho.

Another challenge when flying above the concrete jungle: winds that blow in from as far as Batam and bounce off the buildings.

Col Ho said: 'The winds change very much, but the pilots are quick to make adjustments so that they will not be blown off their flight path.'

But one benefit of flying over buildings is that the pilots can use the rooftops as landmarks.

'It is easier for us to look out for each other and know where we are,' said Lieutenant-Colonel Leng Wai Mun, known as Black Knight 1.

During the six-minute display, the six pilots have only a few seconds between the first four stunts.

Then, they have about 60 seconds to regroup for the finale, when the jets will shoot towards the ground, leaving behind a curtain of smoke.