Mandala 737-200 in a Medan Market

When the Mandala Airlines plane crashed in overcast weather 500m from the airport at Medan in Sumatra - shoving aside cars and motorcycles before ploughing into a row of houses in a fireball - it killed 147 people, many of them on the ground.

It was the sixth major crash in as many weeks and had aviation experts wondering if it was random coincidence or something more disturbing.

In disasters from Greece to Peru, from Sicily to Venezuela, and now in Indonesia, nearly 500 people have lost their lives. And but for a remarkable escape, a further 300 would have died when their Air France Airbus hit the deck at Toronto's Pearson Airport on August 2 in the first of the incidents.

David Learmount, operations and safety editor of the magazine Flight International, is an expert on air safety, and he agrees that the series of accidents is remarkable.

"It's a very, very long time since we've had this many, even in one year, and it's a really freakish time."

But ask him if commercial flight is becoming less safe, as passenger numbers continue to boom and more and more planes take to the skies, and he denies it robustly.

Mandala 737 lies in a Medan marketplace after a port engine failure on take-off

Learmount says modern aircraft are far safer than their predecessors, incorporating key new features such as the enhanced ground proximity warning system, which has eliminated what was the major cause of air passenger death - controlled flight into the ground (a plane hitting a mountain the captain did not know was there.)

Instead, Learmount points to a very different and perhaps uncomfortable conclusion - culture.

He says the less-developed countries have a much less strong safety culture, in every way, than the developed West, and that when this consideration is applied to air transport it means flying on airlines other than the "majors" is simply not as safe.

"Statistics tell us that it's safe to fly, but they also tell us who it's safe to fly with," he says.

"Take these recent crashes - apart from the Air France one, where everybody got out safely, as they were meant to do - and ask yourself if you have even heard of the airlines."

(They are Turinter from Tunisia, Helios from Cyprus, West Caribbean from Colombia, TANS from Peru and Mandala from Indonesia.)

"The answer is that you haven't. This is not surprising, this is fact. There are massively different standards of safety achieved by airlines in different parts of the world.

"African airlines have always been the least safe to fly with. There are exceptions - such as South African Airways and, interestingly enough, Ethiopian Airlines.

"But on the whole they have a pretty awful record. Latin America had been getting better ... but perhaps it's reverting to type, I don't know. And Indonesia has always been poor.

"The advice is and always has been, fly with the majors because they have a superb safety record. But the chances of crashing when you fly with airlines coming from outside western Europe, North America and Australasia are an order of magnitude greater."

ATR72 (fitted with ATR42 fuel gauges) afloat just after ditching off Palermo

Countries that were more modern, politically and economically, had the luxury of a safety culture, which applied to everything, such as road safety, and not just aviation.

"All modern aeroplanes are safe, but they may not be if they don't get maintained properly and the crews don't get trained properly.

"In some countries, crews get trained according to the law, but trained to a minimum standard. Whereas the serious airlines of the world train their crews a damn sight better."

Learmount said the enhanced proximity warning device, mandatory on all new planes for the past decade, made it well-nigh impossible for a captain to fly the aircraft straight into a mountain hidden in cloud.

The digital instrument technology in the cockpit was much more informative and reliable than the old battery of dials which used to face pilots.

"There's no doubt about it, aviation is a lot safer than it used to be."