WASHINGTON (AP) — Interior Secretary Ryan Zinke is strongly defending his use of private charter flights for government business, calling criticism of his travel "complete and utter bull---" that's based on politics. Zinke is defending himself over reports that he took at least three private flights costing taxpayers a total of $20,000 since taking office in March. Zinke says his travel is "legal, ethical. All the trips went through absolute due diligence." Zinke spoke to reporters Wednesday following a boat tour at the Okefenokee National Wildlife Refuge in southeast Georgia. He says that in his job, everything he does "goes through absolute legal review." He says previous Interior secretaries spent even more money on private travel, adding: "I wish you'd publish that. Because I can tell you, they're in the millions."