Snowplow driver Vladimir Martynenko has denied claims by Russian officials that he was drunk
at the time of the crash Monday at Moscow's Vnukovo International Airport.
Total CEO Christophe de Margerie and three others were killed after his plane hit the snowplow during takeoff and crashed.
Four other airport employees have also been detained in connection with the crash, a Russian investigative committee said earlier.
They are: the airport service chief engineer, Vladimir Ledenev, who's in charge of snow-clearing operations; flights director Roman Dunayev; air traffic controller Svetlana Krivsun; and the airport's chief air traffic controller, Alexander Kruglov.
"Investigators believe the detained persons failed to provide safety requirements concerning flights and on-ground works and it led to the tragedy," a statement from the investigative committee said. "They have been detained and questioned as suspects in the case."
Amid the fallout from the incident, the airport's director general, Andrei Dyakov, and deputy director general Sergei Solntsev have resigned, the airport said in a statement Thursday. Their resignations have been accepted.
The airport's shift director, the head of the airport's maintenance division and the leading engineer who heads the shift have been suspended from duties.
Martynenko's lawyer, Aleksandr Karabanov, told CNN that a court decided Thursday to place him in detention.
"The judge explained her decision, saying that the court decided that Martynenko could escape, put pressure on trial participants or destroy the evidence," Karabanov said.
He said the judge had also introduced a doctor's certificate with results of a preliminary medical examination.
She said that according to that data, Martynenko was found to be drunk, but the final results would be known and announced in five to seven days.
"I found it's ridiculous and it makes no sense," Karabanov said. "During that medical examination, Martynenko had a blood test that would show whether there was alcohol in his blood. It always takes only a day or two to get the results. Why are we still not given any?"
He said he was convinced his client was sober at the time.
Karabanov said at a news conference Wednesday that Martynenko had passed a daily "medical examination" that all snowplow operators at the airport are required to take before reporting for duty.
The lawyer said the results of the test were recorded in a log book that investigators now have.
According to the lawyer, Martynenko became separated from a convoy of snowplows after he heard a strange sound and stopped briefly to check his equipment.
The lawyer speculated that an unnamed air traffic controller saw the other snowplows in the convoy and cleared the runway without realizing that Martynenko's machine was still there.
The French government has deployed three investigators and two technical consultants from its aviation authority to also investigate the crash.