Well before Newcastle United’s players and coaches set off for a warm-weather training camp in Saudi Arabia this week, the new owners of the Premier League soccer team were facing the difficult task of persuading the world that the team would not be an asset of the Saudi state.

It has not been an easy case to make: 80 percent of Newcastle, after all, now belongs to the Public Investment Fund, Saudi Arabia’s sovereign wealth fund. The P.I.F.’s chairman is Mohammed bin Salman, Saudi Arabia’s crown prince and de facto ruler.

Even the Premier League has in the past expressed concerns about the connections. It delayed Newcastle’s sale for more than a year until, Premier League officials said, it finally allowed the deal to go through in October after receiving unspecified “legally binding assurances” that the Saudi state would not control the soccer team.

Those questions only returned this week, however, when Newcastle’s players and coaching staff shuffled down the steps of their private charter flight in Jeddah, Saudi Arabia, on Monday. Photographs of the team’s arrival showed the plane was operated by a company called Alpha Star, an aviation business whose parent company was seized by Prince Mohammed after a purge of senior royals and business figures shortly after he emerged as the likely heir to the Saudi throne.

The identity of the company and its seizure were documented as part of a lawsuit in Canada brought by the Saudi state against a former senior intelligence official. Alpha Star and its sister company, Sky Prime, another aviation supplier whose planes carried the group of assassins who killed and dismembered the dissident journalist Jamal Khashoggi in Istanbul in 2018, were seized and transferred to the $400 billion sovereign wealth fund — on the orders of Prince Mohammed, according to legal filings — in 2017.

The documents revealing the link between the aviation companies and the country’s ruler are part of a long running corruption lawsuit brought by a group of Saudi state-owned companies against the former intelligence official Saad Aljabri, a close confidant of Mohammed bin Nayef, a former interior minister whom Prince Mohammed ousted as crown prince in 2017.

But the use of planes — owned by a company created and once contracted by the Saudi state to transport extremists and terrorism suspects — also made it harder, again, for Newcastle’s new British-based owners and executives to claim an arm’s length relationship from their Saudi partners in the P.I.F.

State ownership of clubs has become one of the more contentious topics in European soccer in recent years as Paris St.-Germain and Manchester City have both used the seemingly bottomless wealth of their Gulf owners to reshape the economics and competitive balance of the sport. Newcastle fans generally have welcomed the arrival of Saudi riches — and the potential of an on-field revival — at their club, even as critics have raised questions about foreign influence and human rights concerns.

Before his team left England, Newcastle United’s coach, Eddie Howe, was pressed about the purpose of the team’s weeklong visit to Saudi Arabia. Howe insisted the motivations were purely sporting, an effort to fine tune the team’s preparations in a warm-weather setting ahead of the second half of the season. But the club faced criticism from human rights groups like Amnesty International, which said the trip risked becoming “a glorified P.R. exercise for Mohammed bin Salman’s government.”

On Friday, Howe and his players were reported to have met with representatives of the P.I.F., whose board includes a half-dozen senior Saudi government officials.

“I think it just shows, No. 1, why the sale was problematic in the first place and not separate from the Saudi state,” Adam Coogle, a deputy director with the Middle East and North Africa division at Human Rights Watch, said of the trip. “No. 2, it shows they don’t care. They’re just going to flaunt it. They’re not even trying to pretend this isn’t what it is.”

A spokesman for P.I.F. declined a request for comment. The Premier League and Newcastle United declined similar requests on Friday.

The relationship between Newcastle and Saudi Arabia, though, continues to roil the Premier League. Late last year the league amended its regulations on sponsorships after rivals raised concerns about the prospect of a sudden rush of Saudi Arabian money flowing into the team’s accounts through deals with companies linked to its Gulf ownership.

Under a compromise agreement, the league said it would assess all “related party” sponsorships to ensure the agreements were made in line with fair market value.

Since the takeover, the Premier League’s chief executive, Richard Masters, has deflected questions about his organization’s ability to ensure that Newcastle did not contravene the assurances about its being separate from the state. When he was asked in November how the league would even know if the local ownership group was following the orders of Prince Mohammed, Masters acknowledged that the league could not know.

“In that instance, I don’t think we would know,” he said. “I don’t think it is going to happen. There are legally binding assurances that essentially the state will not be in charge of the club. If we find evidence to the contrary, we can remove the consortium as owners of the club. That is understood.”