Interior Secretary Ryan Zinke on Tuesday blamed the department’s proposal to raise fees at various national parks, in part, on free admission offered to the nation’s veterans, elderly and disabled individuals.

“When you give discounted [rates] to the elderly, veterans, and the disabled and do it by the carload, not a whole lot of people actually pay at our front door,” Zinke told the Senate Energy and Natural Resources Committee, Washington Examiner reports. “One person with a pass and everyone comes in for free. We are looking at ways to have more revenue at the front door at our parks.”

The Interior Department last October proposed raising the entrance fee at 17 national parks during those parks’ five busiest months. The department said the increase would “help ensure that they are protected and preserved in perpetuity and that visitors enjoy a world-class experience that mirrors the amazing destinations they are visiting.”

Sitting before the Senate energy committee, Zinke argued the increase would offer “more flexibility” to the parks themselves.

"We want to make sure the parks remain of value and accessible for America,” Zinke insisted. “That is the promise we will make. I am aware an increase hurts some families, and our interest is not to hurt families.”

In response to Zinke’s testimony, ranking member Sen. Maria Cantwell (D-WA) noted Zinke’s use of chartered planes, telling the interior secretary his concerns for the Interior Department’s budget rings hollow in the face of his extravagant spending.

"While my constituents are hearing about private jet rides and expensive doors, they want to understand why someone is proposing to raise park fees at this level,” Cantwell said. "We should be increasing access," to national parks, she said.

Zinke told Cantwell he “resents” her “insults and innuendos,” telling the Senate committee, "I never took a private jet anywhere.”

The Interior Department's Office of Inspector General is currently investigating “the secretary’s travel,” including “modes of transportation, costs and schedules.”