The storm was too massive to fly around, but rather than turn back, Captain Ivan Korogodin decided to risk flying over the towering clouds.

As the Tupolev-154 approached its maximum operating altitude of 12,000 meters, it stalled, went into an uncontrollable spin and slammed into the ground, killing all 170 on board.

The August 2006 crash of Pulkovo Airlines flight 612 from the Black Sea resort of Anapa to St Petersburg was officially blamed on pilot error. But safety advocates see it as symptomatic of a much deeper problem with Russian aviation: a burgeoning fleet of small, low-budget airlines, under-trained pilots, weak government regulation and a cost-cutting mentality in which pilots who abort flights and landings are sometimes fined.

Russia and the other former Soviet republics had the world's worst air-traffic safety record last year, with an accident rate 13 times the world average, according to the International Air Transport Association.

Last year, 318 people died in two major crashes and eight lesser ones of planes flown by Russian carriers - close to half the world's total of 755 fatalities reported by the International Civil Aviation Organization. The combined death toll in Russia plus the former Soviet republics reached 466 last year. Experts, including pilots who fly the former Soviet skies, say government bodies tolerate practices that are wrecking a once honorable safety record.

They say regulation is lax, while airlines overwork their crews and fine pilots for using too much fuel. Many carriers, critics say, also skimp on crew training and cut corners on maintenance of their aging Soviet- built aircraft and secondhand Western planes.

In Russia's latest air crash on July 29, an An-12 cargo plane belonging to the private Atran carrier slammed into the ground minutes after takeoff from a Moscow airport, killing all seven crew on board. The cause was not clear, but the plane was built 43 years ago and was to be discarded later this year.

State-controlled Aeroflot, privately owned Transaero and some other big airlines have modern planes, skilled crews and world-class safety records, experts agree. But scores of smaller carriers, they allege, cut corners on safety. The rules said flight 612 should have turned back to avoid the storm, yet Korogodin, who had logged more than 12,000 flight hours, pressed on, possibly because he wanted to save fuel.

On the flight recorder he is heard ordering copilot Andrei Khodnevich to take the plane upward while warning it will be very difficult. The cockpit alarm screams as the plane approaches maximum altitude, and the copilot yells "Don't kill me!" before the plane hits the ground.

Airline officials insist their fuel conservation incentives and fines do not apply to extreme conditions and thus do not affect safety. But Oleg Smirnov, who heads the nonprofit Partner of Civil Aviation Foundation, is skeptical. "Naturally no one would admit publicly that flight safety isn't the top priority. But nonprofessionals now in charge of many airlines - former economists, lawyers and even dentists - think only about money," said Smirnov, a veteran pilot who was a deputy aviation minister in Soviet times.

"Some companies keep dossiers recording how much fuel a captain expends on his flights. If he expends extra, he is told: 'You get no bonus now, and if you keep acting like that we shall think whether the company needs you.' That sits deeply in a pilot's brain and guides his actions."

Anatoly Knyshov, a highly decorated test pilot with 41 years' experience, said: "Business managers run for profits and neglect safety."

Some airlines allegedly penalize the crews for failing to land on the first attempt - a practice that may have led to a crash in March of a Tupolev-134 whose pilot hit the ground trying to land in fog even though he could not see the tarmac lights. Six were killed.