Treasury Secretary Steven Mnuchin on Capitol Hill (Brendan Smialowski/AFP/Getty Images)

On his way to lunch with President Trump at the White House on a Thursday in March, a major GOP political contributor and hedge fund billionaire named Nelson Peltz stopped by Treasury Secretary Steven Mnuchin’s office to say hello to him and his chief of staff, Eli Miller.

Miller mentioned to Peltz that he was flying to Palm Beach, Fla., that night to visit his in-laws. Peltz said he was traveling there, too, and offered him a ride in his private jet. After getting a green light from Treasury’s ethics official, Miller accepted the ride, working and emailing on the flight while Peltz slept.

[Hedge fund billionaire flew top Mnuchin aide on private jet to Palm Beach]

With a slew of senior Trump administration officials under scrutiny for their use of luxury air travel, the propriety of this trip came under investigation by the Treasury Department’s inspector general.

His conclusion: The flight to Florida was a perfectly legal “gift,” since the chief of staff and the hedge fund billionaire have been friends since they met on the Trump campaign and no Treasury business was discussed.

But in an environment where many actions by Trump administration officials are under the microscope, just because it’s legal doesn’t mean the optics are good, the watchdog’s office warned.

“The applicable regulations do stress that legal does not always equate to appropriate or wise,” Rich Delmar, counsel to Inspector General Eric Thorson, wrote in a nine-page review of the case released Tuesday and launched after The Washington Post reported on the trip in October.

[Treasury Secretary’s flights totaling $811,000 were legal but poorly justified, watchdog says]

Peltz, a founding partner of New York-based Trian Fund Management, has praised the president’s plan to slash tax rates on businesses and the wealthy, a plan largely designed by senior Treasury officials.

Delmar found no evidence that Peltz offered to fly Miller on his private jet to influence tax policy or other Treasury policy, though. The men are friends who communicate by phone, emails and text messages and occasional meetings about twice a month. Miller “sees Peltz as a mentor,” Delmar wrote.

Peltz also personally paid for the flight and did not expense it to his business, further distancing his gift from questions about conflicts of interest.

“The facts [Miller] presented regarding how he knows Mr. Peltz do appear consistent with the regulation’s definition of a personal relationship, in that while it arose from the political campaign and involved the current Secretary, it appears to have been conducted outside of official channels and topics,” Delmar wrote.

Delmar noted that “… there is no evidence that Mr. Peltz’s access to Treasury officials would be enhanced by his offer, and Mr. Miller’s acceptance, of the plane ride. Mr. Peltz knows Mr. Miller, and indeed the Secretary and the President, already.”

He concluded that “Mr. Miller’s acceptance of the aircraft ride does not appear to have violated applicable law and regulation.”

But he urged caution:

“In an environment of high attention to relationships affecting governmental actions, consideration might well be given to another provision in the gift regulation, which observes Even though acceptance of a gift may be permitted by one of the exceptions contained in this section, it is never inappropriate and frequently prudent for an employee to decline a gift if acceptance would cause a reasonable person to question the employee’s integrity or impartiality. Consideration might also be given to making a written record of ethics advice given in situations that can trigger observations like the foregoing.”