In June, Zinke and his staffers took a four-hour flight from Las Vegas to Kalispell, Mont., aboard a private plane owned by the executives of a Wyoming oil-and-gas exploration firm, aviation and business records show…

The flight cost taxpayers $12,375, according to an Interior Department spokeswoman. Commercial airlines run daily flights between the two airports and charge as little as $300.

The new flight details show how Zinke has mixed political gatherings and personal destinations with his taxpayer-funded work as the head of a federal agency that manages or controls the vast majority of federal land.

Interior Department spokeswoman Heather Swift said Zinke’s charter flights were authorized by ethics officials and booked only when feasible commercial flights were unavailable.