In a corner of the departures area at Rostov airport in southern Russia, a group of about 130 men, many of them carrying overstuffed military-style rucksacks, lined up at four check-in desks beneath screens that showed no flight number or destination.
When a Reuters reporter asked the men about their destination, one said: "We signed a piece of paper – we're not allowed to say anything. Any minute the boss will come and we'll get into trouble.
"You too," he warned.
The chartered Airbus A320 waiting on the tarmac for them had just flown in from the Syrian capital, Damascus, disgorging about 30 men with tanned faces into the largely deserted arrivals area. Most were in camouflage gear and khaki desert boots. Some were toting bags from the Damascus airport duty-free.
The men were private Russian military contractors, the latest human cargo in a secretive airlift using civilian planes to ferry military support to Syrian President Bashar al-Assad in his six-year fight against rebels, a Reuters investigation of the logistical network behind Assad's forces has uncovered.
The Airbus they flew on was just one of dozens of aircraft that once belonged to mainstream European and US aviation companies, then were passed through a web of intermediary companies and offshore firms to Middle Eastern airlines subject to US sanctions – moves that Washington alleges are helping Syria bypass the sanctions.
The flights in and out of Rostov, which no organization has previously documented, are operated by Cham Wings, a Syrian airline hit with US sanctions in 2016 for allegedly transporting pro-Assad fighters to Syria and helping Syrian military intelligence transport weapons and equipment. The flights, which almost always land late at night, don't appear in any airport or airline timetables, and fly in from either Damascus or Latakia, a Syrian city where Russia has a military base.
The operation lays bare the gaps in the US sanctions, which are designed to starve Assad and his allies in Iran's Revolutionary Guard and the Hezbollah militia of the men and materiel they need to wage their military campaign.
It also provides a glimpse of the methods used to send private Russian military contractors to Syria – a deployment the Kremlin insists does not exist. Russian officials say Moscow's presence is limited to air strikes, training of Syrian forces and small numbers of special forces troops.
Reuters reporters staked out the Rostov airport, logged the unusual flights using publicly available flight-tracking data, searched aircraft ownership registries and conducted dozens of interviews, including a meeting at a fashionable restaurant with a former Soviet marine major on a US government blacklist.
Asked about the flights and the activities of Russian private military contractors in Syria, a spokesman for Russian President Vladimir Putin referred Reuters to the Defense Ministry – which didn't reply to the questions. The Syrian government also didn't reply to questions.
In response to detailed Reuters questions, Cham Wings said only that information on where it flies was available on its website.
The flights to Rostov aren't mentioned on the site. But the journeys do appear in online flight-tracking databases. Reporters traced flights between the Rostov airport and Syria from Jan. 5, 2017, to March 11, 2018. In that time, Cham Wings aircraft made 51 round trips, each time using Airbus A320 jets that can carry up to 180 passengers.
The issue of military casualties is highly sensitive in Russia, where memories linger of operations in Chechnya and Afghanistan that dragged on for years. Friends and relatives of the contractors suspect Moscow is using the private fighters in Syria because that way it can put more boots on the ground without risking regular soldiers, whose deaths have to be accounted for.
Forty-four regular Russian service personnel have died in Syria since the start of the operation there in September 2015, Russian authorities have said. A Reuters tally based on accounts from families and friends of the dead and local officials suggests that at least 40 contractors were killed between January and August 2017 alone.
One contractor killed in Syria left Russia on a date that tallies with one of the mysterious nighttime flights out of Rostov, his widow said. The death certificate issued by the Russian consulate in Damascus gave his cause of death as "haemorrhagic shock from shrapnel and bullet wounds."
To sustain his military campaign against rebels, Assad and his allies in Russia, Iran and the Hezbollah militia need access to civilian aircraft to fly in men and supplies. Washington has tried to choke off access to the aircraft and their parts through export restrictions on Syria and Iran and through Treasury Department sanctions blacklisting airlines in those countries. The Treasury Department has also blacklisted several companies outside Syria, accusing them of acting as middlemen.
"These actions demonstrate our resolve to target anyone who is enabling Assad and his regime," John E. Smith, director of the Treasury Department's Office of Foreign Assets Control, said in testimony to a congressional committee in November.
In recent years, dozens of planes have been registered in Ukraine to two firms, Khors and Dart, that were founded by a former Soviet marine major and his onetime military comrades, according to the Ukraine national aircraft register. The planes were then sold or leased and ended up being operated by Iranian and Syrian airlines, according to the flight-tracking data.
One of the companies, Khors, and the former marine major, Sergei Tomchani, have been on a US Commerce Department blacklist since 2011 for allegedly exporting aircraft to Iran and Syria without obtaining licenses from Washington.
But in the past seven years, Khors and Dart have managed to acquire or lease 84 second-hand Airbus and Boeing aircraft by passing the aircraft through layers of non-sanctioned entities, according to information collated by Reuters from national aircraft registers. Of these 84 aircraft, at least 40 have since been used in Iran, Syria and Iraq, according to data from three flight-tracking websites, which show the routes aircraft fly and give the call sign of the company operating them.
In September, the US Treasury Department added Khors and Dart to its sanctions blacklist, saying they were helping sanctioned airlines procure US-made aircraft. Khors and Dart, as well as Tomchani, have denied any wrongdoing related to supplying planes to sanctioned entities.
Four lawyers specializing in US export rules say that transactions involving aircraft that end up in Iran or Syria carry significant risks for Western companies supplying the planes or equipment. Even if they had no direct dealings with a sanctioned entity, the companies supplying the aircraft can face penalties or restrictions imposed by the US government, the lawyers said.
The lawyers, however, said that the legal exposure for aircraft makers such as Boeing and Airbus was minimal, because the trade involves second-hand aircraft that are generally more than 20 years old, and the planes had been through a long chain of owners before ending up with operators subject to sanctions.
Two of the lawyers, including Edward J. Krauland, who leads the international regulation and compliance group at law firm Steptoe & Johnson, said US export rules apply explicitly to Boeing aircraft because they're made in the United States. But they can also apply to Airbus jets because, in many cases, a substantial percentage of the components is of US origin.
Boeing said in a statement: "The aircraft transactions described that are the subject of your inquiry did not involve The Boeing Company. Boeing maintains a robust overall trade control and sanctions compliance program." An Airbus spokesman said, "Airbus fully respects all applicable legal requirements with regard to transactions with countries under UN, EU, UK and US sanctions."
Although Moscow denies it is sending private military contractors to Syria, plenty of people say that's untrue. Among them are dozens of friends and former colleagues of the fighters and people associated with the firm that recruits the men – a shadowy organization known as Wagner with no offices, not even a brass plaque on a door.
It was founded by Dmitry Utkin, a former military intelligence officer, according to people interviewed during this investigation. Its first combat role was in eastern Ukraine in support of Moscow-backed separatists, they said. Reuters was unable to contact Utkin directly. The League of Veterans of Local Conflicts, which according to Russian media has ties to Utkin, declined to pass on a message to him, saying it had no connection to the Wagner group.
Russia has 2,000 to 3,000 contractors fighting in Syria, said Yevgeny Shabayev, local leader of a paramilitary organization in Russia who is in touch with some of the men. In a single battle in February this year, about 300 contractors were either killed or wounded, according to a military doctor and two other sources familiar with the matter.
A Russian private military contractor who has been on four missions to Syria said he arrived there on board a Cham Wings flight from Rostov. The flights were the main route for transporting the contractors, said the man, who asked to be identified only by his first name, Vladimir. He said the contractors occasionally use Russian military aircraft too, when they can't all fit on the Cham Wings jets.
Two employees at Rostov airport talked to Reuters about the men on the mysterious flights to Syria.
"Our understanding is that these are contractors," said an employee who said he assisted with boarding for several of the Syria flights. He pointed to their destination, the fact there were no women among them and that they carried military-style rucksacks. He spoke on condition of anonymity, saying he wasn't authorized to speak to the media.
Reuters wasn't able to establish how many passengers were carried between Russia and Syria, and it is possible that some of those on board were not in Syria in combat roles. Some may have landed in Damascus, then flown to other destinations outside Syria.
Interviews with relatives of contractors killed in Syria also indicate the A320 flights to Rostov are used to transport Russian military contractors. The widow of one contractor killed in Syria said the last time she spoke to her husband by phone was on Jan. 21 last year – the same day, according to flight-tracking data, that a Cham Wings charter flew to Syria.
"He called on the evening of the 21st ... There were men talking and the sound of walkie-talkies. And by the 22nd he was already not reachable. Only text messages were reaching him," said the woman, who had previously visited her husband at a training camp for the contractors in southern Russia.
After he was killed, she said, his body was delivered to Russia. She received a death certificate saying he had died of "hemorrhagic shock from shrapnel and bullet wounds."
The widows of two other contractors killed in Syria described how their husbands' bodies arrived back home. Like the first widow, they spoke on condition of anonymity. They said representatives of the organization that recruited their husbands warned of repercussions if they spoke to the media.
The two contractors had been on previous combat tours, their widows said. The women said they received death certificates giving Syria as the location of death. Reuters saw the certificates: On one, the cause of death was listed as "carbonization of the body" – in other words, he burned to death. The other man bled to death from multiple shrapnel wounds, the certificate said.
One of the widows recounted conversations with her husband after he returned from his first tour of duty to Syria. He told her that Russian contractors there are often sent into the thick of the battle and are the first to enter captured towns, she said.
Syrian government forces then come into the town and raise their flags, he told her, taking credit for the victory.
Sign up for The Top of the World, delivered to your inbox every weekday morning.