By EDDIE WRENN and LUKE SALKELD
Those planes look close: As the Wentworth golf spectators look up, tension begins to mount as the 'larger' plane begins to catch up with the smaller one
Out of the clear blue sky, these two planes look as though they have veered on to a devastating collision course.
Thousands of feet up, the jets appeared so close that horrified spectators at Wentworth golf course thought disaster was inevitable.
But the view for the passengers on board was rather less remarkable. In fact, the relative positions of the planes as they prepared to land at Heathrow is an everyday occurrence.
The plane on the left is actually a mile or two lower than the plane on the right – taking part in a process known as ‘stacking’ as the pilots wait their turn to land. The apparent near-miss was little more than an optical illusion which the crowds at the BMW PGA Championship in Surrey were perfectly placed to witness on Sunday.
As the planes came together, the crowd diverted their attention and watched nervously for catastrophe
There were gasps from the galleries as the planes approached each other and a crash seemed imminent
Moment of 'impact': As the crowd squeezed their collective eyes shut, the planes hit - and the illusion is broken
...And the planes separate, perfectly safe all along, and the crowds realise they had been fooled by an optical illusion - and the golf can continue
A spokesman for air traffic control at Heathrow said: ‘At all times, planes are kept five horizontal miles apart and at least 1,000ft vertically. Even when it looks like the planes are close, there is no danger.’
The London airport is one of the world's busiest, with more than 1,300 flights arriving or leaving each day, and air traffic controllers organise the planes into the stacking procedure.
Naturally, the 'bigger plane' is much closer to the camera, and likely to be a mile or two away from the the 'smaller' plane up above.
Stacking explained: Planes join a queue, always at least 1,000 feet apart vertically-wise and with a five-mile gap horizontally, when waiting for a runway
A spokesman for the Air Traffic Control at Heathrow said: 'We do hear reports of these from time to time - especially in the summer when it is a perfectly clear day and there are no visual reference points, making it appear that two planes are close.
'However at all times, planes are are kept five horizontal miles apart and a least 1,000 feet vertically, and this is monitored by both pilots and radar, so even when it looks like the planes are close, there is no danger.'
So this can be a common enough optical illusion if you live under a flight-path.
But for a group of spectators on a sunny Saturday, it was a heart-stopping few seconds which they are sure to never forget.
Perfectly placed: The crowd were in prime position for the action - unfurling at both ground level and in the skies above
The view from the plane: An aerial photograph of Wentworth Golf Course, where the spectators were based