Soon after joining Donald Trump’s presidential campaign in March 2016, Paul Manafort began trading emails with his “right-hand man” from Ukraine, Konstantin Kilimnik, about their billionaire former business partner, Russian oligarch Oleg Deripaska.

Their relationship with the tycoon had soured. Deripaska had filed complaints against Manafort in court for millions allegedly owed to him. And Manafort was looking for ways to smooth things over.

“How do we use to get whole?” Manafort asked Kilimnik in an April email, noting the press coverage surrounding his new role on the Trump campaign. In July, Manafort followed up on his cryptic question by telling Kilimnik to offer “private briefings” to Deripaska, one of Russian President Vladimir Putin’s closest billionaire allies, according to emails disclosed by The Washington Post.

In August, Manafort and Kiliminik finally met face to face in a ritzy cigar lounge four blocks from Trump Tower.

Now, congressional investigators believe Kilimnik used Deripaska’s private Gulfstream 550 jet for at least one leg of that journey, a person familiar with their findings told VICE News, confirming a report in the Guardian on Friday.

Whether Kilimnik was a passenger on Deripaska’s jet for both directions of its roundtrip between Moscow and Newark in early August 2016 remains unclear, the person said. There is “some discrepancy in the travel log” about one half of the journey, the person told VICE News.

“What knowledge did you have of any outreach ... Russia about potential assistance to the campaign?”

Deripaska has repeatedly denied “any interactions during, after, or in the run-up to the 2016 presidential elections” with Manafort, including any briefings. But congressional investigators’ assertion that Kilimnik used the oligarch’s plane for that August 2016 meeting raises fresh questions about the nature of Manafort’s relationship with Deripaska in the lead-up to the election. Federal investigators have been pouring over the details of that key period for at least two years.

Russian contact

In April, special counsel Robert Mueller reportedly sent a list of four dozen questions to Trump’s lawyers, including an inquiry about Manafort: “What knowledge did you have of any outreach by your campaign, including by Paul Manafort, to Russia about potential assistance to the campaign?”

Kilimnik’s links to the Trump campaign have likewise been carefully scrutinized. FBI agents believe Kilimnik had “ties to a Russian intelligence service” in 2016, Mueller’s team wrote in a court filing earlier this year. Kilimnik, who is reportedly now living in the Moscow suburb of Khimki, has strenuously denied being a Russian spy. He didn’t return an email requesting comment from VICE News for this story.

The use of Deripaska’s jet would suggest that one of Putin’s top oligarch allies knew about both the meeting and the substance of Kilimnik’s discussion with Manafort, said Mary McCord, who led the Justice Department’s investigation into foreign meddling in the 2016 election before stepping down in early 2017.

“If Kilimnik flew to New York on Deripaska's private jet for a meeting with Manafort, that would be of great interest to the special counsel,” McCord told VICE News. “And it certainly suggests that when Kilimnik returned to Moscow, he would have debriefed with the person on whose jet he had just flown.”

A spokesperson for Deripaska declined to comment on Kilimnik or the August flights in an email Monday, and blasted the media for “tabloid-style” coverage.

“It is regrettable to see how unethical some media outlets have become in their effort to spread unverified, partisan and ill-intended nonsense in a tabloid-style manner,” wrote the spokesperson, who asked not to be named. “Most importantly, this has nothing to do with quality journalism and we simply will not engage with any spurious requests.”

Moscow to New York

In March, VICE News first revealed that the jet’s flight from Moscow to Newark, New Jersey, several miles outside Manhattan, had captured investigators’ attention.

At that time, a spokesperson for Deripaska said that the plane was simply carrying members of the Russian billionaire’s family.

“The passengers of the flights during the time period in early August 2016 were Mr. Deripaska’s family only,” the spokesperson, who likewise asked not to be named, wrote in an email to VICE News earlier this year. “Thus, we repeat that any publications implying that Mr. Deripaska directly or indirectly communicated with Mr. Manafort in 2016 would be a false statement of fact.”

But the oligarch’s murky ties to Trump’s former campaign chairman have continued to be of interest to federal investigators. In September 2016, one month after Kilimnik met with Manafort, FBI agents appeared at a home Deripaska maintained in New York and pressed him about whether Manafort “had served as a link between the campaign and the Kremlin,” according to The New York Times.

Deripaska rebuked the FBI’s inquiries, calling their questions about his role in the campaign “preposterous,” The Times reported. He again denied any connections to Manafort during the election season or that Kilimnik flew on his jet to the Guardian on Friday.

“We vigorously deny all these allegations and false information which has no ground and is being plotted by someone who for more than a year has been unsuccessfully trying to develop a story which does not exist,” a spokesperson for Mr. Deripaska told the British newspaper.

In April, Deripaska and other Russian oligarchs were hit with sanctions which the U.S. Treasury Department said were aimed at punishing Russia for its aggressive foreign policy, including attempts to “subvert Western democracies.”

Deripaska has responded with a lobbying campaign to have the sanctions on him and his companies lifted, according to a detailed Times report in early November.

‘Mr. Manafort's money’

Mueller’s prosecutors pursued Manafort vigorously over a bevy of criminal charges mostly unrelated to the 2016 campaign until he finally pled guilty in September, striking a sweeping agreement with the feds to disclose everything he knows.

During his trial in Alexandria, Virginia, prosecutors painted Manafort as a brilliant political strategist driven by greed, who’d successfully parlayed his role on campaigns into tens of millions of dollars. They cast Kilimnik as one of Manafort’s closest lieutenants.

Kilimnik played a key role in Manafort’s Ukrainian exploits as Manafort’s translator and general local fixer, sitting in on important meetings. The two men forged a tight relationship while working for the country’s Russia-friendly former president, Viktor Yanukovych, people who know both men told VICE News.

“He [Kilimnik] got into a really close, father-and-son relationship with Paul [Manafort],” a person who’s known both men for years told VICE News.

At Manafort’s trial, prosecutors said Kilimnik had signatory authority over several of his boss’s hidden offshore bank accounts during those years.

Their work in Ukraine together proved fabulously lucrative, while it lasted. Manafort raked in some $65 million advising Yanukovych between 2010 and 2014 after masterminding Yanykovych’s shocking presidential electoral win, according to evidence presented at his trial.

But when Ukraine’s government collapsed in chaos and Yanukovych fled to Moscow in 2014, Manafort needed new revenue streams to maintain his lavish lifestyle, prosecutors said. In September, he pled guilty to submitting fraudulent applications for multimillion-dollar bank loans during the following years.

Regardless, Manafort offered up his services to the Trump campaign free of charge in February 2016.

Even though he didn’t draw a paycheck from Trump, prosecutors said Manafort found a way to make his political activities work for his wallet. He arranged to take out $16 million in loans from a small Chicago lender called the Federal Savings Bank, while pushing to get that bank’s majority owner and CEO, Stephen Calk, appointed as Trump’s secretary of the Army, prosecutors said.

His lingering business dispute with Deripaska, however, remained unresolved. As the 2016 campaign got underway, Kilimnik assured Manafort that he had forwarded articles about Manafort’s new role on the Trump campaign to a Deripaska aide, The Atlantic reported. Kilimnik wrote: “I am more than sure that it will be resolved and we will get back to the original relationship.”

It hasn’t worked out that way. Companies controlled by Deripaska would eventually pursue Manafort for millions in courts in the Cayman Islands, Virginia and New York.

In January of this year, a company controlled by Deripaska sued Manafort and Gates in New York for at least $25 million in damages connected to a failed joint cable and internet venture in Ukraine, according to court documents.