Expenditure controversies
In September 2017, it was reported that on June 26, Zinke had chartered a jet belonging to an oil industry executive for a flight from Las Vegas to Kalispell, Montana. Zinke had been in Las Vegas to make an announcement related to public lands and to deliver a speech to the National Hockey League's Vegas Golden Knights, an expansion franchise owned by William P. Foley, a major donor to Zinke's congressional campaigns. The chartered flight cost taxpayers $12,375. Costs for commercial flights between Las Vegas and Kalispell typically start at $300. Upon arrival in Kalispell, Zinke spent the night at his private residence before delivering remarks at the annual meeting of the Western Governors Association the next morning. Zinke and his staffers returned to Washington on a commercial flight the next day.
Zinke used private aircraft and performed political duties in relation to an April 1 trip between St. Croix and St. Thomas in the U.S. Virgin Islands. Zinke had been in St. Croix on March 30 for an official meeting with Governor Kenneth Mapp during the day, and spent the night at a fundraiser for the Republican Party of the Virgin Islands, where attendees who pledged between $1,500 and $5,000 were allowed to have their pictures taken with Zinke. The next morning, he took a private flight costing the government $3,150 to St. Thomas to celebrate the centennial of the islands' handover to the United States by Denmark.
In December 2017, Politico reported that Zinke had booked government helicopters for more than $14,000 to travel in June and July 2017. One of these trips was the swearing-in ceremony of his successor in Congress; the Department of Interior defended the use of government helicopters instead of a two-hour car drive by saying Zinke would otherwise not be able to fully participate in the ceremony. An Interior spokesperson also told a Politico reporter asking about the expenses, "Shame on you for not respecting the office of a member of Congress." Another of these trips was the use of a Park Police helicopter to have a horseback ride with Vice President Mike Pence; the Interior Department justified the use of the helicopter over the three-hour car drive by saying, "the Secretary will be able to familiarize himself with the in-flight capabilities of an aircraft he is in charge of" and that Park Police staff would "provide an added measure of security to the Secretary during his travel." Zinke dismissed Politico's reporting as "total fabrications and a wild departure of reality" but did not identify any inaccuracies in the reporting.
In October 2017, the Interior Department's Office of Inspector General (OIG) launched an investigation into Zinke's use of three charter flights during his tenure as Interior Secretary. In April 2018, OIG released its report, concluding that Zinke's chartered flight to give the June 2017 speech to the Las Vegas Golden Knights was authorized "without complete information" and that the speech was not official business because Zinke did not discuss the Interior Department or his role as Interior Secretary. OIG concluded that the two other charter flights, one to Alaska and the other to the U.S. Virgin Islands, "appeared to have been reasonable as related to official DOI business."
In October 2017, the United States Office of Special Counsel launched a Hatch Act investigation into Zinke's meeting with the Vegas Golden Knights.
In a March 2018 Senate Energy and Natural Resources Committee, Zinke said it was false that he had taken a private jet anywhere, noting that the charter flights he took were on aircraft with propellers, not jet engines.
As of October 30, 2018, the OIG had referred Zinke to the Department of Justice for investigation, including of whether he lied to the OIG about his involvement in reviewing a tribal casino project in Connecticut. The two Connecticut tribes claim that the Interior Department refused to sign off on the casino project after intense lobbying by MGM Resorts International and two Nevada Republican lawmakers. Zinke said the OIG interviewed him twice about the casino decision and that he was truthful both times. In late 2019, Deputy Attorney General Jeffrey Rosen stalled the probe into Zinke. Federal prosecutors had proposed to move forward with possible criminal charges against Zinke over his involvement in the casino deal. In doing so, Rosen also prevented the Interior Department's Office of Inspector General from making public a report about the casino deal.