Russia has detained four Moscow airport employees over a plane crash which killed the head of French oil giant Total, whose private jet hit a snowplough on takeoff, investigators said Thursday.
Those detained include the air traffic controller in charge of directing the doomed plane at Vnukovo airport, her supervisor, the head of air traffic controllers and the chief of runway cleaning, Russia's investigative committee said in a statement.
"The investigation suggests that these people did not respect the norms of flight security and ground operations, which led to the tragedy," the statement said. "They have been detained as suspects."
Longtime Total boss Christophe de Margerie was killed along with the crew of his private jet in Monday night's accident.
The driver of the snowplough that collided with the plane has said he had lost his bearings and strayed on to the runway.
The Falcon 50 carrying French oil boss De Margerie crashed Monday night after colliding with a snowplough as it took off from Vnukovo airport, killing the Total chief and three crew.
Here are the latest developments in the probe:
Driver 'not drunk'...
Russian investigators were quick to accuse snowplough driver Vladimir Martynenko of being drunk but a lawyer for the 60-year-old said he does not drink due to a heart condition.
"He took his (heart) medication that morning but I do not think that this could have had an effect," lawyer Alexander Karabanov told Echo of Moscow radio station Wednesday.
... but 'lost'
In footage of his first interrogation broadcast on Russian state television Wednesday, Martynenko said he drove on to the runway after losing his way.
"When I lost my bearings, I myself didn't notice when I drove on to the runway -- that is, let's say I drove out," Martynenko said, appearing calm and speaking clearly.
"The plane was running up to takeoff and I practically couldn't see it because my equipment was on. There weren't even any lights, nothing," he said, shrugging.
"I didn't see it, and the collision happened."
Martynenko's lawyer said the driver had been in a column of snowploughs that had been clearing the area the evening of the crash.
He said Martynenko became separated from his colleagues when he got out to check his vehicle for "30 or 40 seconds" after feeling something was wrong with the snowplough.
According to Martynenko, his lawyer said, the air traffic controller likely did not notice that one of the snowploughs was left back on the runway.
Novice in the control tower?
A source at Vnukovo airport told AFP the air traffic controller overseeing the takeoff of the executive jet was an inexperienced recent recruit.
"It is a young woman who was hired in August," the source said on condition of anonymity.
Russian daily Izvestia quoted an airport source as saying the female controller was an intern who had recently graduated from the civil aviation college in the provincial city of Ulyanovsk. Other media reports however said she was working under the supervision of an experienced colleague, who is known for preventing an air crash in 2007.
Black boxes opened
Russian aviation officials said they had opened the black boxes from the doomed jet and were analysing the crucial data of the flight history and conversations in the cockpit.
The recorders were opened in the presence of specialists from France's accident investigation bureau, said Sergei Zaiko, deputy head of Russia's Interstate Aviation Committee, or MAK.
The information would take about "two to three days" to analyse, an aviation official told Ria Novosti.