Former secretary of energy Ernest Moniz billed taxpayers over $75,000 for a government flight to Mexico City, just weeks before he left office.

The costs of the trip were revealed in a special report released by the department's inspector general Friday, investigating the use of government charter flights in both the Trump and Obama administrations.

Moniz traveled to Mexico City on Jan. 7, 2017, less than two weeks before President Trump was inaugurated. The purpose of the trip was to sign a "non-binding" document on electricity grids.

Tasked with investigating the use of government aircraft by Secretary of Energy Rick Perry, the inspector general identified nine trips by Obama and Trump officials between October 2015 and December 2017, costing $178,000.

Nearly half of those costs came from Moniz's single trip to Mexico.

"We identified six trips from January 2017 through December 2017 that were sponsored by the Department of Energy where the Secretary or other non-career Department Federal officials utilized Government or privately chartered aircraft," the inspector general said. "One of these trips was taken by Secretary Moniz in January 2017 under the previous administration to participate in the signing of the United States-Mexico Bilateral Reliability Principles in Mexico City, Mexico and to attend the opening ceremony of the Waste Isolation Pilot Plant in Carlsbad, New Mexico."

The flights to Mexico City and Carlsbad cost $75,461. The cost for Moniz and 10 other energy officials was $3,018 per traveler per leg.

Moniz also billed taxpayers $3,550 for a flight from Seattle to Richland, Wash., in August 2016.

The inspector general identified other charter flights taken by Deputy Secretary Elizabeth Sherwood-Randall, an Obama energy official, including a $3,209 flight from Portland to Seattle, by way of Electric City, Wash.

Sherwood-Randall also took a flight from Augusta, Ga., to Meridian, Miss., at a cost of $3,093.

Taxpayer-funded charter flights have come under media scrutiny since Trump came into office. Tom Price was forced out of his post at the Department of Health and Human Services for taking numerous private charter flights.

The inspector general, however, found no wrongdoing with Secretary Perry's Department of Energy.

"During our review, nothing came to our attention to indicate that non-career Federal employees within the Department had inappropriately taken trips on Government aircraft," the inspector general said.

"The Department has always believed that there has been no misuse of government aircraft by Secretary Perry and DOE staff," said Shaylyn Hynes, press secretary at the Department of Energy. "We appreciate the Inspector General's review which found nothing improper about the few instances where Secretary Perry and DOE staff have utilized non-commercial travel."

"The IG report confirms that each trip was considered official government business, approved by the Department’s Office of General Counsel as required by OMB Circular A-126," she said.

Perry has taken five government flights, though none have cost as much as Moniz's single trip to Mexico.

Perry's most expensive flights cost an estimated $40,000 to Riyadh, Saudia Arabia, Abu Dhabi, UAE, and to Doha, Qatar, in December. Perry participated in a White House mission to the Middle East for bilateral meetings and discussed possible U.S. exports of liquefied natural gas to Saudi Arabia.

Rep. Frank Pallone (N.J.), the ranking Democrat on the House Energy and Commerce Committee, asked the inspector general to review Perry's government aircraft travel. Democratic members of the committee were "concerned" about Perry's trip to Kansas City in 2017. The inspector general said the trip, where Perry spoke at a small business forum and toured the Kansas City National Security campus, was justified.

"Specifically, the Committee questioned whether Secretary Perry could have used commercial aircraft to fly into Kansas City International Airport," the inspector general said. "We determined that the circumstances of that trip provided a reasonable basis for the exceptional scheduling requirements cited as justification for the trip. Secretary Perry had firmly scheduled events that General Counsel indicated could not have been accommodated by commercial air service."

"We found that the return trip was justified because the Department had to pay the costs to return the aircraft back to its origin regardless of whether it contained passengers," the inspector general added.

In all, Perry's flights on government charter planes have cost $93,112.

"Our review of the schedules for the six trips did not indicate any personal or political stops," the inspector general said, of all the trips taken by Moniz and Perry in 2017.

All nine trips since October 2015 were justified "on the basis of exceptional scheduling requirements," the inspector general said.